THEORY OF HORTICULTURE. 



THE THEORY 



HORTICULTURE: 



AN ATTEMPT TO EXPLAIN 



THE PRINCIPAL OPERATIONS OF GARDENING 



UPON PHYSIOLOGICAL PRINCIPLES. 



JOHN LINDLEY, PH.D. F.R.S., 

VICE-SECRETARY OF THE HORTICULTURAL SOCIETY OF LONDON, AND PROFESSOR OF 
BOTANY IN UNIVERSITY COLLEGE. 



" Though I am very sensible that it is from long experience chiefly that w 
of practice, yet it is withal to be remembered that the likeliest method to 
obsei vat ions, and to put us upon the most probable means of rmproviug an 
into the nature and properties of those things which we ere desirous to culti 
Statics, I. 3/6. 



re to expect the most certain rules 

rt, is to get the best insight we caa 
;e and improve." — Holes'! Vegetable 



SECOND AMERICAN EDITION, WITH NOTES, etc. 



A. J. DOWNING 




NEW YORK: 
JOHN WILEY, 18 PARK PLACE. 



1852. 



Entered according to the act of Congress, in the year 1852, by 

JOHN WILEY, 

In the Clerk's Office of the District Court for the Southern District of New York. 






17 



THE MEMORY 



THOMAS ANDREW KNIGHT. 



PREFACE 



AMERICAN EDITION. 



Within the last ten years, the taste for Horticultural 
pursuits has astonishingly increased in the United States. 
There are, at the present moment, at least twelve societies 
in different parts of the Union devoted to the improvement 
of gardening, and to the dissemination of information on 
this subject. Nor is it surprising that gardening should 
be a favourite pursuit in this country, when we consider the 
fertility of our soil, the ease and abundance in which all the 
finer fruits of temperate climates may be produced, and the 
comparative facility with which individuals may become 
landholders. But although a taste for Horticulture is 
widely diffused, and its practice is frequently very successful, 
yet few of our amateurs or professed cultivators understand 
the rationalia of the operations they pursue ; and hence 
they are unable to improve or modify their methods so 
as to ensure full success under varying circumstances, or 
safely to apply the directions they may receive from books 
or other sources. 



Vill PREFACE TO THE 

The works on Horticulture which have hitherto been 
published in this country, are nearly restricted to details 
of practice, rarely attempting to convey any information 
beyond short directions for the culture of particular crops, 
or monthly memoranda for the management of different 
departments of the garden. Several of these, moreover, 
being chiefly compiled from similar foreign treatises, are by 
no means adapted to our climate, and are consequently 
of little value to the novice in the art of gardening. It 
may, therefore, be presumed that a work like the present, 
which explains those universally applicable principles upon 
which all correct horticultural operations necessarily depend, 
will prove quite as useful to amateurs and cultivators 
generally in this country, as in Great Britain, where it has 
supplied a most important desideratum. It is the only 
treatise of the kind extant, at least in the English language ; 
and probably, no person living is so well qualified for 
preparing such a work as Professor Lindley. It is at once 
remarkably simple, and highly philosophical ; free from 
superfluous technicalities, and at the same time truly 
scientific. Without entering into tedious subordinate 
details, it offers a lucid explanation of the general nature 
of vegetable actions, and of the important principles which 
lie at the foundation of all the operations of Horticulture, 
and which the intelligent gardener or amateur can readily 
apply for himself to each particular case. 

A knowledge of these leading principles, at once invests 
with new and peculiar interest even the most mechanical, 



AMERICAN EDITION. IX 

ai:d apparently unmeaning and irksome details of the art. 
With what increased satisfaction are the common processes 
of manuring or transplanting carried on, to say nothing 
of the more delicate operations of budding, grafting, 
propagating by layers, &c, when we are acquainted with 
the structure of the plants we are endeavoring to control, 
and comprehend the why and the wherefore of every step 
we pursue ! AVith this knowledge of vital actions, new 
modes of culture, and various improvements in the 
operations of the art, are continually suggested to the 
reflective mind ; which derives additional pleasure from the 
prosecution of scientific experiments, of which the ignorant 
laborer, who turns over the soil and sows his seeds in 
precisely the same manner under all circumstances, never 
dreams. 

Besides the higher gratification which Horticulture 
affords, when its principles are understood, the increased 
profit, derived from the superior quality and augmented 
quantity of the products, and the greater certainty of 
success in culture, should not be forgotten. Were the 
labours of the gardener always confined to the same en- 
closure, the same soil, and the same climate, a formal routine 
of practice would frequently produce all the desired results. 
But as scarcely two soils are exactly alike, as the position 
or exposure of a garden has a great influence on its 
productiveness, and as his operations must be varied 
according to varying circumstances to ensure success, how 
important is it that the enterprising cultivator should 
1* 



understand those really simple general principles, founded 
upon the very nature of things, upon which all his under- 
takings are based. Among the simplest operations, it is 
one thing to prune a tree properly, so as to keep it in 
a healthy and productive stale, with just the proper 
proportion of fruit and leaf-buds ; and quite another to cut 
away a certain bulk of wood annually, merely because 
pruning is generally thought a beneficial practice. Similar 
comparisons might be drawn from many familiar cases 
between the injurious results of empirical practice, as 
contrasted with those which follow the application of correct 
principles, and some knowledge of vegetable physiology. 

The notes appended to this edition are rendered necessary 
in some cases, by the difference between the climate of 
England and of this country ; or they relate to different 
applications of principles : it is hoped that they will in some 
degree increase the value of the work to the Americau 
reader. a. j. d. 

Xevburgh, on the Hudson, March, 1852. 

A few notes signed G. were contributed to the first American 
edition by Professor Gray. 



PREFACE 



NGLISH EDITION 



This book is written in the hope of providing the intelligent 
gardener, and the scientific amateur, correctly, with the rationalia 
of the more important operations of Horticulture ; in the full 
persuasion that, if the physiological principles on which such 
operations, of necessity, depend, were correctly appreciated by 
the great mass of active-minded persons now engaged in 
gardening in this country, the grounds of their practice would 
be settled upon a more satisfactory foundation than can at 
present be said to exist. It is, I confess, surprising to me, that 
the real nature of the vital actions of plants, and of the external 
forces by which they are regulated, should be so frequently misap- 
prehended even among writers upon Horticulture ; and that ideas 
relating to such matters, so very incorrect as we frequently find 
them to be, should obtain among intelligent men, in the present 
state of what I may be permitted to call horticultural physiology. 
There must be a great want of sound knowledge of this subject, 
when we find an author, who has made himself distinguished in 
the history of English gardening, giving it as his opinion, " that 



Xll PREFACE TO THE 

the weak-drawn state of forced Asparagus in London is occa- 
sioned by the action of the dung immediately upon its roots ! " 

It does not seem possible to account for this in any other way 
than by referring it to the want of some short guide to the 
horticultural application of vegetable physiology, unmixed with 
other things : and so arranged that the intimate connexion of one 
branch of practice with another, and of the whole with a few 
well ascertained facts upon which everything else depends, may 
be distinctly perceived from a single point of view. The 
admirable papers of Mr. Knight are scattered through the 
Horticultural Transactions ; and the writings of other physiolo- 
gists are dispersed through so many different works, that the 
labor of finding them, when wanted, is greater than is willingly 
undertaken even by those who have access to ample libraries. 
With regard to general works on Horticulture, it is very far 
from my wish to say one word in disparagement of the many 
excellent publications upon this subject which have already 
appeared in this country; on the contrary, the improved state 
of gardening among us may be reasonably ascribed to the 
influence of some of these valuable works : but it must be 
admitted that the true principles of physiology are not, in such 
books, so separated from the details of routine on the one hand, or 
so applied to them on the other, as to be readily understood by 
those who want either the skill or the inclination to distinguish 
empirical directions from rules which are plainly founded upon 
the very nature of things. I must also be permitted to observe 
that, although results are correctly stated in such books, they 
are not unfrequently referred to wrong causes. 

In preparing the following pages for the press, my anxious 
desire has been to strike out all unnecessary matter, even 
although it may be required to complete the physiological 



ENGLISH EDITION. Xlll 

explanation of common facts ; and to introduce little beyond 
that which every gardener can verify for himself. Vegetable 
anatomy is no doubt the foundation of all correct views of 
physiological action ; chemistry is of the first importance, when 
the general functions of plants are considered in a large and 
general way; and electricity probably exercises an important 
influence over the vital actions of all living things. But these 
are the refinements of science, belonging to the philosopher in 
his laboratory, and not to the worker in gardens ; they are 
indispensable to the correct appreciation of physiological 
phenomena, but not to the application of those phenomena to 
the arts of life ; electricity, in particular, appears to me, in the 
present imperfect state of our knowledge of its relation to 
vegetable functions, altogether incapable of forming a part of 
any horticultural theory. 

What the gardener wants is, not a treatise upon botany, nor 
a series of speculations upon the possible nature of the influence 
on plants of all existing forces, nor an elaborate account of 
chemical agencies inappreciable by his senses and obscurely 
indicated by their visible results; but an intelligible explanation, 
founded upon well ascertained facts, which he can judge of by his 
own means of observation, of the general nature of vegetable 
actions, and of the causes which, while they control the powers 
of life in plants, are themselves capable of being regulated by 
himself. The possession of such knowledge will necessarily 
teach him how to improve his methods of cultivation, and lead 
him to the discovery of new and better modes. 

It is very true that ends of this kind are often brought 
about by accident, without the smallest design on the part of 
the gardener ; and there are, doubtless, many men of unculti- 
vated or idle minds, who think waiting upon Providence much 



XJV PKEl'ACE 10 THE 

better than any attempt to improve theif condition by the 
exertion of their reasoning faculties. For such persons, books 
are not written, 

I hope that what has now been said will not lead any one 
to suppose that this sketch is offered to the reader as a 
complete theory of Horticulture in all its varied branches; 
such a work would be alike tedious to the author and the 
reader, and, I fear, as unprofitable ; for, if a gardener, when once 
made acquainted with the general principles of science, has not 
the skill to apply them to each particular case, it is to be feared 
that no disquisition, however elaborate, would enable him to do 
so. So far has it been from my intention to enter into subor- 
dinate details, that I have carefully avoided them, from a fear 
of complicating the subject, and making that obscure which in 
itself is sufficiently clear. All that a physiologist has really to 
do with Horticulture is, to explain the general nature of the 
vital actions of a plant, and the manner in which these are 
commonly applied to the arts of cultivation; if he quits this 
ground, he extends his limits so much that there is no longer a 
horizon in view. No one, indeed, could advantageously inves- 
tigate the minor points of cultivation in all their branches, 
unless he were both a good physiologist and a practical gardener 
of the greatest experience, a combination of qualifications which 
no man has ever yet possessed, and to which I, most assuredly, 
have not the shadow of pretension. 

In conclusion, let me, in impressing upon the minds of gar- 
deners the importance of attending to first principles, also caution 
them against attempting to apply them, except in a limited 
manner, and by way of safe experiment, until they fully under- 
stand them. The difference between failure and success, in 
practice, usually depends upon slight circumstances, very easily 



ENGLISH EDITION. XV 

overlooked, and not to be anticipated beforehand, even by the 
most skilful ; their importance is often unsuspected till an experi- 
ment has failed, and may not be discovered till after many 
unsuccessful attempts, during which more mischief may be done 
by extensive failures than the result is worth when attained. 
No man understood this better than the late Mr. Knight, the 
best horticultural physiologist that the world has seen, whose 
experiments were conducted with a skill and knowledge which 
few can hope to equal. So fully was he aware of the uncertain 
issue of experimental investigations in Horticulture, that he 
thought it necessary, in recommending a new mode of cultivating 
the Pine-apple, and in objecting to methods at that time commonly 
in use, to express himself in the following words : — " I beg to 
be understood that I condemn the machinery only which our 
gardeners employ, and that I admit most fully their skill in the 
application of that machinery to be very superior to that which I 
myself possess. Nor do I mean, in the slightest degree, to 
censure them for not having invented better machinery, for it is 
their duty to put in practice that which they have learned ; and, 
having to expend the capital of others, they ought to be cautious 
in trying extensive experiments, of which the results must 
necessarily be uncertain ; and, I believe, a very able and experi- 
enced gardener, after having been the inventor of the most 
perfect machinery, might, in very many instances, have lost both 
his character and his place before he had made himself 
acquainted with it, and consequently become able to regulate 
its powers." 



CONTENTS. 



BOOK I. 

Page 

Of the Principal Circumstances connected with Vegetable 
Life which illustrate the Operations of Gardening . . 5 

CHAPTER I. 

GERMINATION. 

The Nature of a Seed. — Its Duration. — Power of Growth. — 
Causes of Germination. — Temperature. — Light, — Humidity. 
— Chemical Changes . . . . . . . .7 

CHAPTER II. 

GROWTH BY THE ROOT. 

Roots lengthen at their Points only. — Absorb at that Part 
chiefly. — Increase in Diameter like Stems. — Their Origin. — 
Are feeding Organs. — Without much Power of selecting their 
Food. — Nature of the latter. — May be poisoned. — Are con- 
stantly in Action. — Sometimes poison the Soil in which they 
grow. — Have no buds. — But may generate them . . . 10 

CHAPTER m. 

GROWTH BY THE STEM. 

Origin of the Stem. — The Growing Point, — Production of 
Wood, Bark, Pith, Medullary Rays. — Properties of Sap-wood, 
Heart-wood, Liber, Rind, &c. — Nature and Office of Leaf- 
buds. — Embryo-buds. — Bulbs. — Conveyance of Sap, and its 
Nature 22 



XV111 CONTENTS. 

CHAPTER IV. 

Pagi 

action of leaves. 

Their Nature, Structure, Veins, Epidermis, Stoniates. — Effect of 
Light. — Digestion or Decomposition of Carbonic Acid. — 
Insensible Perspiration. — Formation of Secretions. — Fall of 
the Leaf. — Formation of Buds by Leaves . . . .8*7 

CHAPTER V. 

ACTION OF FLOWERS. 

Structure of Flowers. — Names of their Parts. — Tendency of the 
Parts to alter and change into each other, and into Leaves. — 
Double Flowers. — Analogy of Flowers to Branches. — Cause 
of the Production of Flowers. — Of Productiveness. — Of 
Sterility. — Uses of the Parts of a Flower. — Fertilisation. — 
Hybrids. — Crossbreds 55 

CHAPTER VL 

OF THE MATURATION OF THE FRUIT. 

Changes' it undergoes. — Superior and inferior Fruit — Is fed by 
Branches upon organisable Matter furnished by Leaves. — 
Physiological Use of the Fruit — Nature of Secretions. — The 
Changes they undergo. — Effect of Heat. — Of Sunlight — Of 
Water. — Seeds. — Origin of their Food. — Cause of their Lon- 
gevity. — Of their Destruction. — Difference in their Vigour . 69 

CHAPTER VII. 

OF TEMPERATURE. 

Limits of Temperature endurable by Plants. — Effects of a too 
high Temperature. — Of a too low Temperature. — Frost — 
Alternations of Temperature. — Day and Night. — Winter and 
Summer. — Temperature of Earth and Atmosphere . .79 



CONTENTS. xiX 



BOOK II. 

Page 
Of the Physiological Principles upon which the Operations 
of Horticulture essentially depend .... 101 

CHAPTER I. 
Of Bottom Heat 102 

CHAPTER II. 
Of the Moisture of the Soil. — Watering .... 113 

CHAPTER III. 
Of Atmospherical Moisture and Temperature . . . 125 

CHAPTER IV. 
Of Ventilation 150 

CHAPTER V. 
Of Seed sowing 159 

CHAPTER VI. 
Of Seed-saving 169 

CHAPTER VII. 
Of Seed-packing 1*79 

CHAPTER VIH. 
Of Propagation by Eyes and Knaurs 184 

CHAPTER IX. 
Of Propagation by Leaves ....... 190 

CHAPTER X. 
Of Propagation by Cuttings 199 

CHAPTER XI. 
Of Propagation by Layers and Suckers .... 207 



XX CONTENTS. 

CHAPTER XII. 

Page 

Of Propagation by Budding and Grafting . . . .210 

CHAPTER XHI. 
Of Pruning 289 

CHAPTER XIV. 
Of Training 256 

CHAPTER XV. 
Of Potting .... 267 

CHAPTER XVL 
Of Transplanting 2*79 

CHAPTER XVIL 
Of the Preservation of Races by Seed 295 

CHAPTER XVIH. 
Of the Improvement of Races 306 

CHAPTER XIX 
Of Resting 818 

CHAPTER XX 
Of Soil and Manure 881 

Index 845 



THE THEORY 



HORTICULTURE 



INTRODUCTION. 



1. Horticulture is that branch, of knowledge 
which relates to the cultivation, multiplication, and 
amelioration of the Vegetable Kingdom. It divides 
into two branches, which, although mutually depen- 
dent, are, in fact, essentially distinct : the art and the 
science. Under the art of horticulture is compre- 
hended whatever concerns the mere manner of exe- 
cuting the operations connected with cultivation, mul- 
tiplication, and amelioration ; the science explains the 
reasons upon which practice is founded. It is to the 
consideration of the latter subject that the following 
pages are dedicated. 

2. It must have been remarked by all intelligent 
observers, that in the majority of works upon hor- 
ticultural subjects, the numerous directions given in 
any particular ramification into which the art is sus- 

1 



2 INTRODUCTION. 

ceptible of being divided, are held together by no 
bond of union, and that there is no explanation of 
their connexion with general principles, by which 
alone the soundness of this or that rule of practice 
may be tested ; the reader is therefore usually oblig- 
ed to take the excellence of one mode of cultivation 
and the badness of another, upon the good faith of 
gardening authors, without being put into possession 
of any laws by which they may be judged of before- 
hand. Horticulture is by these means rendered a 
very complicated subject, so that none but practised 
gardeners can hope to pursue it successfully ; and, 
like all empirical things, it is degraded into a code of 
peremptory precepts. 

3. It will nevertheless be found, if the subject is 
carefully investigated, that in reality the explanations 
of horticultural operations are simple, and free from 
obscurity ; provided they are not encumbered with 
speculations, which, however interesting they may 
be in theory, are only perplexing in practice, in the 
present state of knowledge. When, for example, 
chemical illustrations, unless of the simplest kind, 
or minute anatomical questions, or references to the 
agency of the electrical fluid, are discussed, the sub- 
ject becomes embarrassed with considerations which 
are too refined for the apprehension of the majority 
of readers of gardening works, and which have little 
obvious application to practical purposes. Instead, 
therefore, of introducing points of obscure or doubt- 
ful application, or such as are not absolutely requi- 
site for the explanation of phenomena, all which ne- 
cessarily tend to complicate the theory of horticul- 



INTRODUCTION. 3 

ture, it seems better strictly to confine our attention 
to the action of the simplest vital forces ; for the gene- 
ral nature of these has been undoubtedly ascertained, 
and is easily understood by every class of readers. 
It is certain, for instance, that plants breathe, digest, 
and perspire ; but it may be a question whether the 
exact nature of their respiration, digestion, and per- 
spiration is beyond all further explanation : it is 
therefore better to limit our consideration to the na- 
ked fact, which is all that it imports the gardener to 
know, without inquiring too curiously into those phe- 
nomena. For it must always be remembered, that 
the object of a work like the present is not to eluci- 
date the laws of vegetable life in all their obscure 
details, but to teach, to those acquainted with the art 
of gardening, what the principles are upon which 
their practice is founded. 

4. In order to attain this end, it is necessary, in the 
first place, to explain briefly, but distinctly, the na- 
ture of those vital actions which have a direct refer- 
ence to cultivation ; omitting everything that tends 
to embarrass the subject, or which is not susceptible 
of a direct practical application ; and in the next 
place, to show how those facts bear upon the routine 
of practice of the horticulturist, by making them ex- 
plain the reason of the treatment which is employed 
in various branches of the gardener's art. 

5. The first part of this work will therefore em- 
brace the principal laws and facts in vegetable phy- 
siolog}^, as deduced from the investigations of the 
botanist ; and the second, the application of those 



4 INTRODUCTION. 

laws to practice, as explained by the experience of 
the horticulturist. 

6. If the laws comprehended in the first book are 
correctly explained, and the facts connected with 
them rightly interpreted, they must necessarily afford, 
in all cases, the reasons why one kind of cultivation 
is better than another ; and all kinds of practice at 
variance with those laws must be bad. Since, from 
the very nature of things, this cannot be otherwise, 
it follows that, by a careful consideration and due un- 
derstanding of these laws, the intelligent cultivator 
will acquire the most certain means of improving his 
practice. 



BOOK I. 

OF THE PRINCIPAL CIRCUMSTANCES CONNECTED 
WITH VEGETABLE LIFE WHICH ILLUSTRATE THE 
OPERATIONS OF GARDENING. 

7. A plant is a living body composed of an irrita- 
ble, elastic, hygrometrical matter, called tissue. It is 
fixed to the earth by roots, and it elevates into the 
air a stem bearing leaves, flowers, and fruit. It has 
no power of motion except when it is acted upon by 
wind or other external forces ; it is therefore peculiar- 
ly susceptible of injury or benefit from the accidental 
circumstances that may surround it ; and, having no 
free agency, it is above all other created beings suited 
to acknowledge the power of man. 

8. In order to turn this power to account, it is ne- 
cessary to study the manner of life which is peculiar 
to the vegetable kingdom, and to ascertain what the 
laws are by which the numerous actions essential to 
the existence of a plant are regulated. It is, more- 
over, requisite that the causes which modify those ac- 
tions, either by increasing or diminishing their force, 
should be understood. 

9. The vital actions of plants have so little resem- 
blance to those of animals, that we are unable to ap- 
preciate their nature, in even the smallest degree, by 
a reference to our own sensations, or to any know- 
ledge we may possess of animal functions. Nor, 



6 VITAL ACTIONS. 

when we have thoroughly studied the phenomena of 
vegetation, are we able to discover any analogies, ex- 
cept of a general and theoretical nature, between the 
animal and vegetable kingdoms. It is therefore ne- 
cessary that plants should be studied by themselves, 
as an abstract branch of investigation, without at- 
tempting to reason as to their habits from what we 
know of other organic beings ; and consequently we 
are not, in this part of Natural History, to acknow- 
ledge any theory which is not founded upon direct 
experiment, and proved by the most satisfactory 
course of inquiry. 

10. In discussing this subject, it will be most con- 
venient for my present purpose, if I divide the mat- 
ter into the heads of, 1. Germination ; 2. Growth by 
the Koot ; 3. Growth by the Stem ; 4. Action of the 
Leaves ; 5. Action of the Flowers ; and, 6. Matura- 
tion of the Fruit. By this means the life of a plant 
will be traced through all its principal changes, and 
it will be easy to introduce into one or other of these 
heads every point of information that can be interest- 
ing to the cultivator ; who will be most likely to seek 
it in connexion with those phenomena he is best 
acquainted with by their effects. 



GERMINATION. 



CHAPTER I. 
GERMINATION. 



The Nature of a Seed. — Its Duration.— Power of 
Growth. — Causes of Germination. — Temperature. — 
Light. — Humidity. — Chemical Changes. 

11. A seed is a living body, separating from its 
parent, and capable of growing into a new individual 
of the same species. It is a reproductive fragment, 
or vital point, containing within itself all the elements 
of life, which, however, can only be called into ac- 
tion by special circumstances. 

12. But while it will with certainty become the 
same species as that in which it originated, it does not 
possess the power of reproducing any peculiarities 
which may have existed in its parent. For instance, 
the seed of a Green Gage plum will grow into a new 
individual of the plum species, but it will not pro- 
duce the peculiar variety called the Green Gage. 
This latter property is confined to leaf-buds, and 
seems to be owing to the seed not being specially or- 
ganized after the exact plan of the branch on which 
it grew, but merely possessing the first elements of 
such an organization, together with an invariable 
tendency towards a particular kind of developement. 

13. Under fitting circumstances a seed grows ; that 
is to say, the embryo which it contains swells, and 



8 VITAL ACTIONS. 

bursts through its integuments ; it then lengthens, 
first in a direction downwards, next in an upward 
direction, thus forming a centre or axis round which 
other parts are ultimately formed. ISTo known power 
can overcome this tendency, on the part of the em- 
bryo, to elevate one portion in the air, and to bury the 
other in the earth ; but it is an inherent property with 
which nature has endowed seeds, in order to ensure 
the young parts, when first called into life, each find- 
ing itself in the situation most suitable to its exist- 
ence ; that is to say, the root in the earth, the stem 
in the air. 

14. The conditions required to produce germina- 
tion are, exposure to moisture, and a certain quantity 
of heat ; in addition, it is necessary that a communica- 
tion with the atmosphere should be provided, if ger- 
mination is to be maintained in a healthy state. A 
seed, when fully ripe, contains a larger proportion of 
carbon than any other part, and so long as it is thus 
charged with carbon, it is unable to grow. The only 
means it possesses of ridding itself of this principle, 
essential to its preservation, but forming an impedi- 
ment to its development as a new plant, is by con- 
verting the carbon into carbonic acid ; for which 
purpose a supply of oxygen is necessary. It cannot 
obtain oxygen in sufficient quantity from the air, for 
it is cut off from free communication with the air by 
various means, either natural, as being enclosed in a 
thick layer of pulp, or in a hard shell or stone ; or ar- 
tificial, as being buried to a considerable depth below 
the surface of the soil. It is from the water absorbed 



GERMINATION. 9 

in germination that the seed procures the requisite 
supply of oxygen ; fixing hydrogen, the other ele- 
ment of water, in its tissue : and thus it is enabled to 
form carbonic acid, which it parts with by its respira- 
tory organs, until the proportion of fixed carbon is 
lowered to the amount suited to its growth into a 
plant. 

15. But the formation and respiration of carbonic 
acid takes place most freely, though not exclusively, 
in darkness ; if exposed to light, the seed again parts 
with some of its oxygen, and again fixes its carbon 
by the decomposition of its carbonic acid. 

16. In addition to this, the absorption of water 
causes all the parts to soften and expand ; many of 
the dry, but soluble, parts to become fluid ; sap, or 
vegetable blood, to be formed ; and a sort of circula- 
tion to be established, by means of which a commu- 
nication is maintained between the more remote parts 
of the embryo. 

17. Heat seems to set the vital principle in action, 
to expand the air contained in the numerous micro- 
scopic cavities of the seed, and to produce a distension 
of all the organic parts, which thus have their irrita- 
bility excited, never again to be destroyed except with 
death. What degree of heat seeds find most condu- 
cive to their germination, probably varies in different 
species. Chickweed (Alsine media) and Groundsel 
(Senecia vulgaris) will germinate at a temperature 
but little above 32° Fahr. 

18. Germination being established by the absorp- 
tion and decomposition of water, and by the requisite 

1* 



10 VITAL ACTIONS. 

elevation of temperature, all the parts enlarge, and 
new parts are created, at the expense of a mucilagi- 
nous saccharine secretion which the germinating seed 
possesses the power of forming. With the assistance 
of this substance, the root, technically called the radi- 
cle, at first a mere point, or rather rounded cone, 
extends and pierces the earth in search of food ; the 
young stem rises and unfolds its cotyledons, or rudi- 
mentary leaves, which, if they are exposed to light, 
decompose carbonic acid, fix the carbon, become 
green, and, by processes hereafter to be explained, 
when speaking of leaves, form the matter by which 
all the pre-existing parts are solidified. And thus a 
plant is born into the world ; its first act having been 
to deprive itself of a principle (carbon) which, in 
superabundance, prevents its growth ; but, in some 
other proportion, is essential to its existence. 



CHAPTER II. 
GROWTH BY THE ROOT. 

Hoots lengthen at their Points only. — Absorb at that Part 
chiefly. — Increase in Diameter like Stems. — Their 
Origin. — Are feeding Organs. — Without much Power 
of selecting their Food. — Nature of the latter. — May be 
poisoned. — Are constantly in Action. — Sometimes 

. poison the Soil in which they grow. — Have no buds. — 
But may generate them. 

19. The root, being the organ through which food 



GROWTH BY THE ROOT. 11 

is conveyed from the earth into the plant, is the part 
which is the soonest developed. Even in the embryo, 
at the earliest commencement of germination, it is the 
part immediately connected with the root that first 
begins to move, by lengthening all its parts, and pro- 
truding itself beyond the seed-coats into the earth. 

20. But as soon as this primitive lengthening of the 
root has taken place, and the upper part of the embryo, 
namely the young stem, has begun to exist as a sepa- 
rate organ, the root changes its propert}*, ceases to grow 
by a general distension of its tissue, and simply in- 
creases in length by the addition of new matter to its 
point. A root is therefore extended much in the same 
way as an icicle, by the constant superposition of 
layer over layer to its youngest extremity; with this 
difference, however, that an icicle is augmented by 
the addition of matter from without, while the root 
lengthens by the perpetual creation of new matter 
from within. 

21. For this reason, the extreme points of the roots 
are exceedingly delicate, and are injured by very 
trifling causes ; they, moreover, as all newly formed 
vegetable matter is extremely hygrometrical, have 
the power of absorbing, with rapidity, any fluid or 
gaseous matter that may be presented to them. On 
this account they are usually called spongelets* 

22. In the roots of ordinary Exogens,* when the 

* [For an explanation of this term, see note under paragr. 50.] 



12 VITAL ACTIONS. 

tissue is very young, the spongelet (Jig. 1. a) consists 




of very lax tender cellular tissue, resting upon a blunt 
cone of woody matter, composed principally of woody 
tubes, and connected with the alburnum* of the stem 
(fig. 1. b) ; it is, therefore, placed in the most favour- 
able position possible for communicating to the gene- 
ral system of circulation the fluids taken up by its 
highly absorbent tissue. 

^ 23. It is the opinion of most vegetable physiolo- 
gists, that the absorbing or feeding powers of roots 
are conducted principally at these points ; and that 
the general surface of the root possesses little or no 
power of the kind. And, indeed, it seems highly 
probable that this is so, when we consider that the 
bark of the root, through whose thickness all fluids 
would have to pass before they reach the alburnum, 
has at least two offices to perform, either of which 
might be interfered with by a current fluid setting 
through it. One of those offices is to convey in a 
downward direction, or to store up, the matter which 
has descended to the roots from the branches and 

* [Or sap-wood. Vid. paragr. 49.] 



GROWTH BY THE ROOT. 13 

leaves ; the other is to give off such superfluous mat- 
ter as it is necessary for its health that the plant 
should part with. 

24. But although there can be no doubt that the 
spongelets act as absorbents with more force than any 
other part of the root, yet it is equally certain that 
the whole surface of young roots also possesses an 
absorbing property, only in a more limited degree. 
It is not until their tissue is solidified that roots be- 
come incapable of passing fluid through their sides ; 
and when very young and soft, there is probably but 
little difference between their action and that of the 
spongelets themselves ; for it is to be remembered 
that the latter are not special organs, but are only the 
very youngest part of the root. 

25. The absorbent power of the spongioles must be 
much greater than would have been supposed, if we 
consider that it is almost entirely through their action 
that the enormous waste of fluid, which takes place 
in plants by perspiration, is made good ; and hence 
their importance to plants, and the danger of destroy- 
ing them, become manifest. 

26. The spongioles and youngest parts of roots are 
found to be rich in nitrogen, a principle once sup- 
posed to be unknown in the vegetable kingdom ; and 
it seems that a supply of this gas is indispensable. to 
their healthy condition. 

27. Eoots being furnished with the power of per- 
petually adding new living matter to their points, are 
thus enabled to pierce the solid earth in which they 
grow, to insinuate themselves between the most 



14 VITAL ACTIONS. 

minute crevices, and to pass on from place to place 
as fast as the food in contact with them is consumed. 
So that plants, although not locomotive like animals, 
do perpetually shift their mouths in search of fresh 
pasturage, although their bodies remain stationary. 

28. The only known exceptions to the rule that 
roots do not lengthen by a general distension of their 
tissue, occur in parts growing in air or water, which 
are non-resisting media, or in certain endogenous 
trees, whose roots lengthen to such a degree as to 
hoist the trunk up into the air off the ground, with 
which it at first was level. 

29. It is not, however, merely in length that the 
root increases ; if such were the case, all roots would 
be mere threads. They also augment in diameter, 
simultaneously with the stem, and under the influence 
of exactly the same causes. Neither is it by an em- 
bryo alone that roots are formed. A plant, once in 
a state of growth, has the power of producing roots 
from various parts, especially from its stem, and from 
older roots. 

30. The immediate cause of the formation of roots 
is involved in obscurity, and is one of the most im- 
portant parts of vegetable physiology still to be in- 
vestigated with reference to horticulture. We all 
know how difficult it is to cause the cuttings of some 
kinds of plants to produce young roots, and how ra- 
pidly they are emitted by others ; it is to be supposed, 
that the difficulty would be diminished in all such 
cases, if we knew exactly under what circumstances 
roots are formed. Nothing, however, sufficiently cer- 



GROWTH BY THE ROOT. 15 

tain and general to merit quotation has yet been as- 
certained concerning this important subject, except 
the following facts, viz. that roots are most readily, 
if not exclusively, formed in darkness and moderate 
moisture ; that they are not, like branches, the de- 
velopement of previously formed buds, but appear 
fortuitously and irregularly from the woody rather 
than the cellular part of a plant ; and that their pro- 
duction is in some way connected with the presence 
of leaves or leaf-buds, because portions of a stem 
having neither leaves nor leaf-buds produce roots un- 
willingly, if at all ; and that such roots perish if their 
appearance be not speedily followed by the formation 
of leaves. Thus, although the first appearance of the 
root in the embryo plant, at the time of germination, 
precedes the expansion of the seed-leaves, yet the 
root will not live unless the seed-leaves are enabled 
to act. 

31. But although the immediate cause of the for- 
mation of roots is unknown, the remote cause is appa- 
rently the elaboration of organisable matter by the 
leaves ; for there can be no doubt that the develope- 
ment of roots is much assisted by the descending sap. 
When a ring of bark is removed from a branch, 
if the wound is wrapped in damp moss, roots will 
invariably push from the upper lip of the wound, 
while the lower will produce none ; a fact so well 
known, that it has been one of the causes of an opi- 
nion, that roots are bundles of wood liberated from 
the central perpendicular system, and that the wood 



16 VITAL ACTIONS. 

itself is nothing but a mass of roots formed by the 
leaves and buds. 

32. The principal office of the root is to attract 
food from the ground. For this purpose it is fur- 
nished, as has been seen, with an extremely hygrome- 
trical point, or spongelet, which is capable of absorb- 
ing incessantly whatever matter of a suitable kind 
may lie in its neighbourhood. Its force of absorption 
is always proportioned to the quantity of food that a 
plant requires : when the sap is consumed rapidly by 
the leaves, as in the spring, the roots are in rapid 
action also ; and as the summer advances, and the 
leaves require a smaller quantity of food, the roots 
become more and more torpid. 

33. The proportion borne by the root to the stem 
is very variable. In such plants as succulent Euphor- 
bias, and probably in all plants whose perspiring 
powers are feeble, the roots are much smaller than 
the stem ; but, in others, the circle occupied by these 
organs must be very much greater than that of the 
branches. In young Oaks this is well known to be 
the case, but the disproportion diminishes as such 
plants advance in age. 

34. There is no period of the year when the roots 
become altogether inactive, except when they are 
actually frozen. At all other times, during the win- 
ter, they are perpetually attracting food from the 
earth, and conveying it into the interior of the plant, 
where it, at the season, is stored up till it is required 
by the young shoots of the succeeding year. The 



GROWTH BY THE ROOT. 17 

whole tissue of a plant will therefore become dis< 
tended with fluid food by the return of spring, and 
the degree of distension will be in proportion to the 
mildness and length of the previous winter. As the 
new shoots of spring are vigorous or feeble in pro- 
portion to the quantity of food that may be prepared 
for them, it follows, that the longer the period of 
rest from growth, the more vigorous the vegetation 
of a plant will become when once renewed, if that 
period is not excessively protracted. 

35. Powerful as the absorbing action of roots is 
found to be, those organs have little or no power of 
selecting their food ; but they appear, in most cases, 
to take up whatever is presented to them in a suffi- 
ciently attenuated form. Their feeding property 
depends upon the mere hygrometrical force of their 
tissue, set in action in a peculiar manner by the vital 
principle ; this force must be supposed to depend 
upon the action of capillary tubes, of which every 
part of a vegetable membrane must, of necessity, con- 
sist, although they are, in all cases, invisible to the 
eye, even aided by the most powerful microscopes. 
Whatever matter is presented to such a set of tubes 
will, we must suppose, be attracted through them, 
provided its molecules are sufficiently minute ; and, 
as we have no reason to believe that there is, in gene- 
ral, any difference in the size of the molecules of 
either gaseous matter or fluids consisting principally 
of water, it will follow that one form of such matters 
will be absorbed by the roots of plants as readily as 
another. For this reason, plants are peculiarly liable 



18 VITAL ACTION'S. 

to injury from the presence of deleterious matter 
in the earth ; and it is probable that, if in many- 
cases they reject it, it is because it does not acquire a 
sufficient state of tenuity ; as in the case of certain 
coloured infusions. 

36. But although this appears to be a general rule, 
there are some exceptions of importance. If a Pea 
and a grain of Wheat are placed side by side in earth 
of the same kind, and made to grow under the same 
circumstances, the Wheat plant will absorb silex in 
solution from the earth, and the Pea will absorb 
none ; whence it would seem that the Pea is unable 
to receive a solution of flint into its system, and that, 
consequently, it possesses what amounts, practically, 
to a power of selection. In like manner, Dr. Dau- 
beny has proved the Pelargoniums, Barley, and the 
Winged Tea (Tetragonolobus) will not receive stron- 
tian ; and it is mentioned in Saussure, that he could 
not make Polygonum Persicaria absorb, by its roots, 
a solution of acetate of lime, although it took up mu- 
riate of soda (common salt) freely. 

37. It is a curious fact, that the poisonous sub- 
stances which are fatal to man are equally so to 
plants, and in nearly the same way. So that, by pre- 
senting opium or arsenic, or any metallic or alkaline 
poison, to its roots, a tree may be destroyed as readily 
as a human being. 

38. The natural food of plants consists of carbon 
in the state of carbonic acid, of nitrogen, certain 
earths and salts, and water. The latter, if distilled, 
has little power, by itself, of sustaining vegetable 



GROWTH BY THE ROOT. 19 

life: but, as in nature it is universally mixed with 
various other substances, it conveys to the roots the 
organisable matters that are required; and it fur- 
nishes, by its decomposition, a considerable supply 
of the oxygen consumed in the formation of carbonic 
acid, and all the hydrogen that is incorporated in the 
tissue of plants.* It has been proved, experimen- 
tally, that plants cannot long exist upon pure water ; 
but if they are so circumstanced as to be able to 
obtain and decompose carbonic acid, they will grow 
in the absence of other matters. It is only, however, 

* [The natural food of plants consists of water holding in solution 
a quantity of carbonic acid and ammonia: the two former, viz. car- 
bonic acid and water, are absolutely indispensable to the support of 
vegetable life ; the latter is equally essential to complete develope- 
ment and for the formation of particular organs or products. In 
assimilating their food, vegetables extract hydrogen from the water, 
and carbon from the carbonic acid ; the oxygen of both being 
restored (either wholly or in part, according to the kind of product 
which is formed,) to the atmosphere from which both were derived. 
The statement in the text, that water " furnishes, by its decomposi- 
tion, a considerable supply of the oxygen consumed in the formation 
of carbonic acid," is very ambiguous, if not altogether incorrect ; 
since plants do not form, but decompose or consume carbonic acid ; 
and they do not consume oxygen, except very partially, and in the 
formation of some of their products ; for, even in the formation of 
those products which contain most oxygen (such as the vegetable 
acids) from their universal food, a portion of oxygen is liberated. 
Water is not only an essential portion of the food of plants, inas- 
much as it furnishes all the hydrogen they consume ; but also 
the vehicle by which the other elements they require, nitrogen, and 
a certain (but variable and more less essential) quantity of saline or 
earthy matters, are conveyed into their system. — We shall have 
occasion to return to the consideration of this subject in a note upon 
Chap. XX. G.j 



20 VITAL ACTIONS. 

when the peculiar principles, whether earthy or 
saline, on which they naturally feed, are presented to 
them, that they become perfectly healthy ; and espe- 
cially when they have the means of obtaining nitro- 
gen, which appears, from its great abundance in the 
youngest parts, to be indispensable to plants upon 
the first formation of their tissue.* 

39. In addition to their feeding properties, f roots 
are the organs by which plants rid themselves of the 
secreted matter which is either superfluous or delete- 
rious to them. If you place a plant of Succory 
in water, it will be found that the roots will, by 
degrees, render the water bitter, as if opium had been 
mixed with it ; a Spurge will render it acrid ; and a 
leguminous plant mucilaginous. And, if you poison 
one half of the roots of any plant, the other half will 
throw the poison off again from the sj^stem. Hence 
it follows, that, if roots are so circumstanced that 
they cannot constantly advance into fresh soil, they 
will, by degrees, be surrounded by their own excre- 
mentitious secretions. 

40. It would also seem to follow that, under the 

* Mr. Riggs states that those seeds of the same kind, which con- 
tain the largest quantity of nitrogen, germinate the earliest. He 
found nitrogen in young roots having the proportion of one to five 
of carbon. Theodore de Saussxu'e also ascertained that germinating 
seeds absorb this gas. 

f According to Mr. Knight, the roots of trees retain the original 
vigour of the variety, after the trunks have become debilitated ; or, 
to use his own words, the powers of life do not become expended 
so soon in roots as in bearing branches. (See ffort TVans., voL 
ii. p. 252.) 



GKOWTH OF THE STEM. 21 

circumstances just named, they would be poisoned, 
because they have little power of refusing to take up 
whatever matter is presented to them in a fitting 
state (35.) But it is by no means certain that the 
excrementitious matter of all plants is poisonous 
either to themselves or to others ; and therefore the 
consequences of roots growing in soil from which 
they cannot advance are uncertain, and only to be 
judged of by actual inquiry into the nature of the 
secretions.* 

41. In general, roots have no buds, and are, there- 
fore, incapable of multiplying the plant to which they 
belong. But it constantly happens, in some species, 
that they have the power of forming what are called 

* There is some difference of opinion among physiologists, 
whether excrementitious matter is thrown off from crops in so con- 
siderable a quantity as to affect succeeding*crops injuriously, or 
whether the difficulty of growing successive crops upon the same 
spot arises from the exhaustion of certain specific elements from the 
soil needfn! to the growth and perfection of one crop, but not neces- 
sary of another. It is more likely that the incapacity of soils to 
bear the same crop for a long series of years suspends partly or both 
these causes ; but the fact that while wheat cannot be raised but 
four or five times in succession from ordinary soils and that on the 
other hand in certain deep alluvial soils of the west excellent crops 
of this grain have been taken twenty or more years in succession 
would go far to prove that the necessity of a change of crops arises 
more from the exhaustion of the particular food required for that 
crop than from the injurious accumulation of excrementitious matter. 
However this may be, the practice of rotation of crops, the best 
possible one for keeping the soil of either the farm or garden in 
good condition, is based upon the fact that plants require change 
of soil whether our object is to raise the largest product, or to do so 
at the least outlav of manure. 



22 VITAL ACTIONS. 

adventitious buds ; and, in such cases, they may be 
employed for the purposes of propagation. There 
is no rule by which the power of a plant to generate 
such buds by its roots can be judged of; experiment 
is therefore necessary, in all cases, to determine the 
point. 



CHAPTEK III. 

GROWTH BY THE STEM. 

Origin of the Stem. — The growing Point — Production 
of Wood, Bark, Pith, Medullary Rays. — Properties 
of Sap-wood, Heart-wood, Liber, Rind, &c., — Nature 
and Office of Leaf -buds. — Embryo-buds. — Bulbs. — 

Conveyance of Sap, and its Nature. 
• 

42. As soon as the root is fully in action, which is 
shortly after it has begun to lengthen, the vitality of 
the living point that exists at the bottom of the seed- 
leaves is excited, and a stem begins to be formed. 
At first the stem is a mere point of living matter, often 
invisible to the eye, but sometimes partially develop- 
ed ; in which latter case it is called the plumule. But, 
as soon as nutritive matter is conveyed into it by the 
nascent root, all its parts receive an impulse, which 
forces them into a growth upwards ; what matter 
already exists is distended, enlarged, and solidified ; 
new matter is rapidly generated in all directions from 
the vital centre, and, if it were not for the current 
setting upwards from the root, it would possibly 



GROWTH BY THE STEM. 23 

grow into a spherical figure. Pressed upon, how- 
ever, by the surrounding earth, impelled upwards by 
the current of sap ascending from the root, and 
attracted into the air by the necessity it feels of respi- 
ration, the young stem assumes a cylindrical form, its 
sides having a tendency to solidify, and its point 
to grow longer. This point, or plumule, or first leaf- 
bud, soon attracts to itself the food which the root 
procures from the earth, and a part of the nutritive 
matter which is stored up in the seed-leaves. It feeds 
especially upon the latter until the store is exhausted, 
and by the time this happens it is clothed with leaves, 
which are themselves able to feed it after the seed- 
leaves have perished. In brief, the stem is a branch 
produced by the first leaf-bud which the embryo 
plant possesses. 

43. When the stem is first called into existence, it 
is merely a small portion of cellular tissue : an organic 
substance, possessing neither strength nor tenacity, 
and altogether unsuited to the purposes for which 
the stem is destined. If such matter formed exclu- 
sively its solid contents, the stem would have neither 
toughness nor strength, but would be brittle like 
a mushroom, or like those parts of plants of which 
cellular tissue is the exclusive component ; such, for 
example, as the club-shaped spadix of an Arum, or 
the soft prickles of a young Eose branch. Nature, 
however, from the first moment that the rudiment of 
a leaf appears upon the growing point of a stem, 
occupies herself with the formation of woody matter, 
consisting of tough tubes of extreme fineness, which 



24 VITAL ACTIONS. 

take their rise in the leaves, and which, thence pass- 
ing downwards throngh the cellular tissue, are incor- 
porated with the latter, to which they give the 
necessary degree of strength and flexibility. In trees 
and shrubs, they combine intimately with each other, 
and so form what is properly called the wood and 
inner bark ; in herbaceous and annual plants, they 
constitute a lax fibrous matter. No woody matter 
appears till the first leaf, or the seed-leaves, have 
begun to act ; it always arises from their bases ; it 
is abundant, on the contrary, in proportion to the 
strength, number, and development of the leaves; 
and in their absence is absent also. 

44. When woody matter is first plunged into the 
cellular tissue of the nascent stem, it forms a circle 
a little within the circumference of the stem, whose 
interior it thus separates into two parts ; namely, the 
bark or the superficial, and the pith or the central, 
portion ; or, in what are called Endogens, into a 
superficial coating analogous to bark, and a central 
confused mass of wood and pith intermingled. The 
effect of this, in Exogens, is, to divide the interior of 
a perennial stem into three parts, the pith, the wood, 
and the bark. 

45. As the cellular tissue of the stem is not sensi- 
bly lengthened more in one direction than in ano- 
ther, and as it is the only kind of organic matter that 
in stems increases laterally, it is sometimes con- 
venient to speak of it under the name of the horizon- 
tal system ; and, for a similar reason, to designate the 
woody tubes which are plunged among it, and which 



GROWTH BY THE STEM. 25 

only increase by addition of new tubes having the 
same direction as themselves, as the perpendicular 
system. 

46. Wood properly so called, and liber or inner 
bark, consist, in Exogens, of the perpendicular sys- 
tem, for the most part ; while the pith and external 
rind or bark are chiefly formed of the horizontal sys- 
tem. The two latter are connected by cellular tissue, 
which, when it is pressed into thin plates by the 
woody tubes that pass through it, acquires the name 
of medullary rays. It is important, for the due expla- 
nation of certain phenomena connected with cultiva- 
tion, to understand this point correctly; and to 
remember that, while the perpendicular system is 
distributed through the wood and bark, the horizon- 
tal system consists of pith, outer bark, and the medul- 
lary processes which connect these two in Exogens, 
and of irregular cellular tissue analogous to medul- 
lary rays in Endogens. So that the stem of a plant 
is not inaptly compared to a piece of linen, the hori- 
zontal cellular system representing the woof, and the 
woody system the warp. 

47. Whenever the stem is wounded, the injury is 
repaired by the cellular or horizontal system, which 
forms granulations that eventually coalesce into 
masses {fig. 2. a), within which the perpendicular 
system or woody matter is subsequently developed. 
Thus the restoration of the communication be- 
tween the two sides of an annular excision is effect- 
ed by granulations of the upper and lower lips, and 
of the medullary rays, which finally run together 

2 



26 



VITAL ACTIONS. 



over the wood (fig. 2. b), and form a coating, below 
which new liber and alburnum may be generated. 
In cuttings, the " callus," 2 

which forms at the end pla- 
ced in the ground, is the 
cellular horizontal system, 
preparing for the reception 
of the perpendicular sys- 
tem, which is to pass down- 
wards in the form of roots. 
Many plants will endure 
extensive lacerations of 
their surface, and close up 
such wounds with great 
facility. The well known 
fact of large inscriptions 
cut in trees below the bark 
(which inscriptions were 
effected by removing very 
broad spaces of the bark and wood) being covered 
over in time by new bark and wood, so as to be 
no longer visible from the outside, sufficiently proves 
this. In such cases, however, the reparation of the 
injury takes place chiefly, if not exclusively, by the 
annual addition of new matter to the lips only of the 
wound, the effect of which is to reduce the circle 
annually to a less diameter, till at last the centre is 
closed up. 

48. In the bark of trees and shrubs two distinct 
parts are found : the one external and cellular ; and 
the other internal, resting upon the wood, and con- 




GROWTH BY THE STEM. 27 

sisting of woody matter mixed with cellular. The 
external is the rind or cortical integument, the inter- 
nal is the liber. These two parts grow independently 
of each other, by their inner faces ; the rind belong- 
ing exclusively to the horizontal system, the liber 
composed of the perpendicular and horizontal systems 
intermixed. 

49. In all Exogenous plants whose stems acquire 
an age beyond that of a very few years, the wood is 
distinguishable into two parts, heart-wood, and sap- 
wood or alburnum. The former is more or less cen- 
tral, and coloured brown or some dark tint ; the lat- 
ter is external, pale yellow, and much softer. Heart- 
wood was originally alburnum, and altered its nature 
with age, in consequence of the solid matter with 
which all its tubes and vessels were choked up ; al- 
burnum is the youngest wood, with all its communi- 
cations free and open, no solid matter having had 
time to accumulate within them. The reason why 
solid matter collects in the tubes of wood, so as gra- 
dually to choke them up, is this : the wood is the 
channel through which all the fluid matter of a plant, 
whether crude or digested, passes, in its way upwards 
to the leaves, or in its horizontal direction from the 
bark to the central parts of the stem. When sap 
leaves the earth and passes into the stem, it ascends 
by the woody matter of the finest fibres of the root ; 
having left them, it flows into the new wood from 
which those fibres emanated, and passes along this 
until it reaches the leaves ; on its return from them 



28 VITAL ACTIONS. 

it descends through the liber, in part passing off hori- 
zontally towards the centre through the medullary 
rays. Wherever it passes it deposits a portion of its 
solid parts ; and, consequently, that portion of the 
wood, namely, the oldest or the heart-wood, through 
which it has passed the most frequently, will have the 
greatest quantity of matter accumulated within it, 
independently of all other reasons for its hardening. 

50. The stem of a plant consists, then, of the fol- 
lowing parts, viz. : 1. Wood, the oldest of which is 
heart- wood, and the newest alburnum ; and this is the 
substance through which sap ascends : 2. Bark, the 
external coating, down the liber or inner face of which 
sap descends : 3. Pith, a central portion of the hori- 
zontal system : and, 4. Medullary Rays, serving to 
connect the rind with the pith, to hold all the parts 
together, and to maintain a communication between 
the centre and the circumference of a stem. The 
stems of all plants have these four parts more or less 
evident. They are most visible in European trees or 
shrubs, in any of which they can be distinctly ob- 
served ; they are least apparent in annual and herba- 
ceous plants, because their lines of separation are not 
defined, all the four parts adhering to each other so 
firmly as to render it difficult to separate them ; and 
in Endogens they are all mixed together, in conse- 
quence of the manner of growth of those plants not 
requiring the same kind of arrangement of parts as is 
indispensable in Exogens.* This will be sufficiently 

* As this work excludes every thing botanical that does not 



GROWTH' BY THE STEM. 29 

illustrated by the comparison of the stems of an Oak, 
a Cabbage, and an Asparagus. 

51. Tubers, the root-stock of the Iris and Ginger, 
what are called the roots (cormi) of the Colchicum 
and Crocus, are all so many different forms of 
stem. 

52. It is the property of a stem, during its growth, 
to form upon its surface, at irregularly increasing or 
diminishing distances, minute vital points of the same 
nature as that in which the stem itself originated. 
Each of those points becomes, or may become, a leaf- 
directly bear upon horticultural purposes, I have not explained the 
difference between Exogens and Endogens; 'wishing the reader to 
refer for information upon all such points to works upon pure bo- 
tany. Nevertheless, as these words are of frequent occurrence, I 
may as well state that they denominate the two greatest classes in 
the vegetable kingdom, to one or other of which almost all the 
flowering plants of common occurrence are referable, and that they 
derive their names from the peculiarity of their manner of growth. 
Exogexs (literally outside-growers) are plants whose woody matter is 
augmented annually by external additions below the liber, and, 
consequently, they are continually enclosing within their centre the 
woody substances formed in previous years ; to such plants, a lateral 
communication between the centre and the circumference, by means 
of medullary rays, seems necessary. Endogexs (literally inside- 
groicers) are plants whose woody matter is augmented annually by 
internal additions to their centre ; and, consequently, they are con- 
tinually pushing to their circumference the woody substance formed 
in previous years. 

[All the trees or shrubs of the United States, except the few Palms 
of our southern confines, are examples of Exogens : the Palms afford 
the best example of Endogens, while the stem of an Asparagus ex 
hibits a similar structure in an herb. A. G.] 



30 VITAL ACTIONS. 

bud, capable of forming other stems or branches like 
that on which it appeared ; and each is protected and 
nourished by a leaf which springs from the bark im- 
mediately below the bud. Such leaf-buds are the 
parts that enable a stem, when reduced to the state 
of a cutting, to produce a new individual like itself; 
and, without them, no propagation by portions of the 
stem could take place. 

53. Leaf-buds are capable, under fitting circum- 
stances, of growing when separated from their mother 
branch, whether they are planted in the earth, or in- 
serted below the bark of a kindred species. In the 
former case, they emit roots into the soil ; in the lat- 
ter, they produce wood, which adheres to the wood 
on which they may be placed. Under ordinary cir- 
cumstances, leaf-buds will not form anywhere except 
at the axils * of leaves; but occasionally they appear 
from other parts, such as the root, the spaces of the 
stem which lie between the leaves (the internodes), 
and even from the leaves themselves. In all such 
cases, they are termed adventitious, because of the un- 
certainty of their appearance. A very remarkable 
state of them is the embryo-bud, a name applied to the 
Jcnaurs, knurs, nodules, or hard concretions, found in 
the bark of various trees, which seem to have, occa- 
sionally, the power of propagating the individual, 
notwithstanding their deformed and indurated 
state. 

* The axil is the acute angle formed by a leaf and stem, at the 
origin of the former ; all bodies growing -within that angle are said 
to be axillary. 



GEOWTH BY THE STEM. 



31 



54. Bulbs are buds of a particular kind, larger 
than common, containing an unusual quantity of se- 
creted matter, and separable, spontaneously, from the 
part which bears them. They are magazines in which 
certain plants store up the nutritive matter collected 
from the leaves. The identity of a bulb and a bud, 
in all essential circumstances, is obvious, if the bud of 
any tree {fig. 4.) is compared with the bulbs of the 
Tiger Lily {fig. 3.). 




55. As leaf-buds are thus the parents of wood, one 
of the means of propagating the individual to which 
they belong, the origin of branches, and consequently 
the source of the developement of leaves themselves, 
they may be considered the most important organs of 
vegetation, so far as any one organ can be called most 
important where all are so mutually dependent the 
one on the other, and so powerfully concur in main- 
taining the system of vegetable life, that it is difficult 



32 VITAL ACTIONS. 

to abstract one part without impairing the efficiency 
of the remainder. 

56. The office of the stem is, to convey the crude 
fluid obtained by the roots from the soil, and called 
sap, into the leaves for elaboration, and then to re- 
ceive it back again. Sap is, originally, water contain- 
ing various gases, earths, and salts, in solution : but, 
as soon as it enters the stem, it dissolves the vegeta- 
ble mucilage it finds there, and becomes denser than 
it was before ; it is further changed by the decompo- 
sition of a part of its water, acquires a saccharine 
character, and, rising upwards through the alburnum, 
takes up any soluble matter it passes through. Its 
specific gravity keeps thus increasing till it reaches 
the summit of the branches ; and, by degrees, it is 
all distributed among the leaves. In the leaves it is 
altered, and then returned into the stem ; not, how- 
ever, into the alburnum, where it would meet the as- 
cending current, but into the bark, through which it 
falls, passing off horizontally through the medullary 
rays into the interior of the stem, and fixing itself in 
the interior of the bark, especially of the root. It 
may be said, that, in trees, the alburnum and liber 
have each two equally important offices to perform : 
the alburnum giving strength and solidity to the stem, 
and conveying sap upwards ; the liber not only con- 
veying sap downwards, but covering over the albur- 
num, protecting it from the air, and enabling it to 
form without interruption. It is, therefore, indispen- 
sable to the healthy condition of plants, that neither 
the alburnum nor the liber should be injured. The 



GROWTH BY THE STEM. 3S 

central wood is of little consequence, and may be de- 
stroyed, as it constantly is in hollow trees ; and the 
rind is of comparatively small importance, for it is 
continualty perishing under the influence of the at- 
mosphere : but the liber and alburnum are naturally 
in a state of constant renovation, and cannot be per- 
manently injured without injury to the plant. 

57. But although, under ordinary circumstances, 
the sap of Exogens rises through the alburnum and 
descends through the liber, yet the simplicity of 
structure in plants is such, that, together with the per- 
meability of their tissue, it enables them, in cases of 
emergency, to alter their functions, and to propel 
their fluids by lateral instead of longitudinal commu- 
nications. The trunk of a tree has been sawed 
through beyond the pith in four opposite directions ; 
namely, from north to south, from west to east, from 
south to north, and from east to west, at intervals of 
a foot, so as completely to cut off all longitudinal com- 
munication between the upper and lower parts of 
the stem, as effectually as if those two parts had been 
dissevered ; and yet the propulsion of the sap from 
the roots into the head of the tree went on as before : 
which could only have been effected by a lateral 
transmission of this fluid through, or between, the 
sides of the woody tissue. So when " ringing" is 
practised, and the alburnum is partially destroyed, 
the ascending fluid diverges into the stratum of wood 
beneath the annulation ; and, when it has passed by, 
it again returns into its accustomed channels ; at the 
same time, it is probable, although not proved, that 
2* 



34 



VITAL ACTIONS. 



some portion of the descending sap forces its way 
laterally below the wound, out of the bark into the 
alburnum, using the latter as a means of communi- 
cating with the bark below the ring. 

Some curious experiments upon this subject were 
contrived by Mr. N. INTiven (Gardener's Magazine, vol. 
xiv.) In one case, he di- 5 

vested the stem of a tree 
of a deep ring of bark, and 
of the first twelve layers of 
wood below it (Jig. 5.) ; ne- 
vertheless the tree continu- 
ed to live and be healthy. 
From the exposed surface 
of the wood no sap made 
its appearance, except from 
a cut which had been in- 
advertently made with the 
saw on one side, to the 
depth of, perhaps, five or 
six layers of wood beyond 
the twelve actually remov- 
ed. From that cut a flow 
of sap took place, and continued to run during the 
whole of the season in which the operation was per- 
formed. In this case, the sap must have ascended 
exclusively by the alburnum.* 




* [This is a possible case ; but the American, familiar with the 
practice of girdling trees, (which is nothing more than ringing with 
the hatchet,) so common in the new settlements, well knows that it 
destroys vitality as certainly as cutting down the tree at once. It 



GROWTH BY THE STEM. 35 

In another case, by making four deep and wide in- 
cisions into the trunk of a tree {fig. 6,), and removing 

6 




the centre, the upper part of the trunk was placed 

may be assumed that the removal of any ring of bark, so broad that 
the wound cannot be healed over in a single season, will cause the 
death of the tree. — During the deep snows of winter, in the northern 
States, young apple-orchards are often destroyed by field-mice, which 
girdle the trees near the ground, and they perish in the course of the 
ensuing season. The trees may however be preserved, by taking a 
suitable circle or section of bark, in the spring, from the limb of 
another apple-tree, and adapting it carefully to the wounded bark, 
the edges of which are to be pared to an even line, and the whole 
bound up and covered with grafting clay It is not absolutely ne- 
cessary that the bark introduced should encompass the whole trunk ; 
as the union by a single portion will preserve the life of the tree, 
and the remainder of the wound will gradually become covered with 
new bark A. J. D.] 



36 VITAL ACTIONS. 

upon four separate pillars of bark and alburnum ; 
and the tree upon which the operation was performed 
continued to live for two years, after which it was 
not observed. In the latter instance, no doubt can 
be entertained that the whole of the ascending sap 
was directed into the four pillars of alburnum, which 
were allowed to remain. 

58. The cause of the flow of the sap appears to be 
the attraction of it by the leaves, which continually 
diminish its quantity ; and the necessity that the sap 
abstracted should be replaced by a further supply 
sent upwards from the roots. The consequence of 
this is, that sap always begins to flow at the ends of 
the branches, a circumstance which has led to the 
erroneous idea that it proceeds from above downwards 
through the alburnum. The flow of the sap must 
not, however, be confounded with the motion of the 
sap, which takes place in the winter as well as in the 
summer, and is a mere impletion of the system, caused 
by the attraction of the roots, unaffected by the ex- 
halation of the leaves. 



ACTION OF LEAVES. 37 



CHAPTEK IV. 
ACTION OF LEAVES 



Their Nature, Structure, Veins, Epidermis, Stomates. — 
Effect of Light. — Digestion or Decomposition of 
Carbonic Acid. — Insensible Perspiration. — Forma- 
tion of Secretions.— Fall of the Leaf. — Formation of 
Buds by Leaves. 

59. A leaf is an appendage of the stem of a plant, 
having one or more leaf-buds in its axil. In those 
cases where no buds are visible in the axil, they are, 
nevertheless, present, although latent, and may be 
brought into developement by favourable circum- 
stances. As this is a universal property of leaves, to 
which there is no known exception, it follows that all 
the modifications of leaves, such as scales, hooks, 
tendrils, &c, and even the floral organs, hereafter to 
be described, have the same property. 

60. Considered with respect to its anatomical struc- 
ture, a leaf is an expansion of the bark, consisting of 
cellular substance, among which are distributed veins. 
The former is an expansion of the rind ; the latter 
consist of woody matter arising from the neighbour- 
hood of the pith, and from the liber.. As the tissue 
forming veins has a double origin, it is arranged in 
two layers, united firmly during life, but separable 
after death, as may. be seen in leaves that have been 



38 VITAL ACTIONS. 

lying for some time in water. Of these layers, one is 
superior and arises from the neighbourhood of the 
pith, the other inferior and arises from the liber ; the 
former maintains a connexion between the wood and 
leaf; the latter establishes a communication with the 
bark. As sap, or ascending fluid, rises through the 
wood, and principally the alburnum, afterwards de- 
scending through the liber, it follows from what has 
been stated, that a leaf is an organ of which the upper 
system of veins is in communication with the as- 
cending, and the lower system with the descending, 
current of sap. 

61. A leaf has moreover a skin, or epidermis, 
drawn all over it. This epidermis is often separable, 
and is composed of an infinite number of minute cavi- 
ties, originally filled with fluid, but eventually dry 
and filled with air. In plants growing naturally in 
damp or shady places it is very thin ; in others, in- 
habiting hot, dry, exposed situations, it is very hard 
and thick ; and its texture varies between the two 
extremes, according to the nature of the species. The 
epidermis is pierced by numerous invisible pores, 
called stomates, through which the plant breathes 
and perspires. Such stomates are generally largest 
and most abundant in plants which inhabit damp and 
shady places, and which are able to procure at all 
times an abundance of liquid food ; they are fewest 
and least active under the opposite conditions. It 
will be obvious, that, in both these cases, the struc- 
ture of a leaf is adapted to the peculiar circumstan- 
ces under which the plant to which it belongs natu- 



ACTION OF LEAVES. 39 

rally grows. Now, as this structure is capable of 
being ascertained by actual inspection with a micro- 
scope, it follows, as a necessary consequence, that the 
natural habits of an unknown plant may be judged 
of with considerable certainty by a microscopical ex- 
amination of the structure of its epidermis. The rule 
will evidently be, that plants with a thick epidermis, 
and only a few small stomates, will be the inhabitants 
of situations where the air is dry and the supply of 
liquid food extremely small ; while those with a thin 
epidermis, and a great number of large stomates, will 
belong to a climate damp and humid ; and interme- 
diate degrees of structure will indicate intermediate 
degrees of atmospherical and terrestrial conditions. 
It is, however, to be observed, that the relative size 
of stomates is often a more important mark in inves- 
tigations of this nature than their number ; those or- 
gans being in many plants extremely numerous, but 
small and apparently capable of action in a very lim- 
ited degree ; while in others^ where they are much 
less numerous, they are large and obviously very ac- 
tive organs. Thus the number of stomates in a 
square inch of the epidermis of Crinum amabile is 
estimated at 40,000, and in that of Mesembryanthe- 
mum at 70,000, and of an Aloe at 45,000; the first 
inhabiting the damp ditches of India, the last two 
natives of the dry rocks of the Cape of Good Hope : 
but the stomates of Crinum amabile are among the 
largest that are known, and those of Mesembryanthe- 
mum and Aloe are among the smallest ; so that the 
70,000 of the former are not equal to 10,000 of the 



40 VITAL ACTIONS. 

Crinum. Again, the Yucca aioifolia has four times 
as many stomates as a species of Cotyledon in my 
collection, but those of the latter are about the yj^ 
of an inch in their longer diameter, large and active, 
while the stomates of the Yucca are not more than 
2jVo of an i QCn long in the aperture, and compara- 
tively inert. The Yucca, therefore, with its nume- 
rous stomates, has weaker powers of perspiration and 
respiration than the Cotyledon. 

62. A leaf, then, is an appendage of the stem of a 
plant, consisting of an expansion of the cellular rind, 
into which veins are introduced, and enclosed in a 
skin through which respiration and perspiration take 
place. It is in reality a natural contrivance for ex- 
posing a large surface to the influence of external 
agents, by whose assistance the crude sap contained 
in the stem is altered and rendered suitable to the 
particular wants of the species, and for returning into 
the general circulation the fluids in their matured 
condition. In a word, the leaf of a plant is its lungs 
and stomach, traversed by a system of veins. 

63. As the leaf is an extension of the rind of a 
stem, its epidermis is also an extension of the skin of 
the same part ; and hence it is that in plants which 
produce no true leaves, such as the Stapelia, the 
office of the leaf is performed by the rind and epider- 
mis of the bark. 

64. The functions of respiration, perspiration, and 
digestion, which are the particular offices of leaves, 
are essential to the health of a plant ; its healthiness 
being in proportion to the degree in which these func- 



ACTION OF LEAVES. 41 

tions are duly performed. Consequently, whatever 
tends to impede the free action of leaves, tends also 
to diminish the healthiness of a plant. 

65. These functions are performed by means of the 
vital forces of vegetation, which we cannot estimate 
or comprehend, assisted by the influence of an exter- 
nal agent, the nature of whose action may be under- 
stood from its effects. That agent is solar light. 

66. It is the property of solar light, when striking 
upon the leaf of a plant, to cause : 1. A decomposi- 
tion of carbonic acid ; 2. An extrication of nitrogen ; 
and, 3. Insensible perspiration. By their vital forces 
plants appear to decompose water, independently of 
the action of light. 

67. Carbonic acid is originally introduced into the 
interior of a plant, either dissolved in the water it 
imbibes by its roots, or by attraction from the atmo- 
sphere, or by the combination of the oxygen obtained 
by a decomposition of water or otherwise, with the 
carbon in its interior. When a leaf is exposed to the 
direct influence of the sun, it gives off oxygen, by 
decomposing the carbonic acid ; whereupon the car- 
bon remains behind in the interior of the leaf in a 
solid state. Although the nature of the air thus ex- 
tricated can only be determined by a chemist, yet the 
extrication itself can be easily seen by any one who 
will plunge a leaf in water and expose it to the sun ; 
for bubbles of oxygen will be seen to form themselves 
upon the surface of the leaf. But, if the same leaf 
be observed in the total absence of solar light, there 
will be little or no extrication of air, and what little 



42 VITAL ACTIONS. 

is given off will be found to be carbonic acid, which 
plants exhale at all times in small quantities ; oxygen, 
however, which was before expelled, is inhaled. 
Hence plants decompose carbonic acid during the 
day, and form it again during the night, the oxygen 
they inhale at that time entering again into combina- 
tion with their carbon ; and, during the healthy state 
of a plant, the decomposition by day, and recomposi- 
tion by night, of this gaseous matter, is perpetually 
going on.* The quantity of carbonic acid decomposed 

* [This absorption of oxygen and recom posit ion of carbonic acid 
during the night, might perhaps be left out of the account in a gene- 
ral view of the subject^ except as an explanation of the manner in 
which plants are injured or destroyed by the protracted absence of 
light. According to the celebrated chemist from whom the following 
remarks are cited, this process is not at all connected with the life 
or growth of vegetables, but is entirely chemical. — " It is true that 
the decomposition of carbonic acid is arrested by the absence of light 
But then, namely at night, a true chemical process commences, in 
consequence of the action of the oxygen in the air upon the organic 
substances composing the leaves, blossoms, and fruit. . . . The 
substances composing the leaves of different plants being known, it 
is a matter of the greatest ease and certainty to calculate which of 
them, during life, should absorb most oxygen by chemical action, 

when the influence of light is withdrawn Whilst the 

tasteless leaves of Agave Americana absorb only 0'3 of their volume 
of oxygen, in the dark, during 24 hours, the leaves of the Pinut 
Abies, which contain volatile and resinous oils, absorb 10 times; 
those of Quercus Robur containing tannic acid 14 times; and the 
balmy leaves of the Populus alba 21 times that quantity. This 
chemical action is shown very plainly, also, in the leaves of the Co- 
tyledon calycinum, the Cacalia Jieoides, and others; for they are sour, 
like sorrel, in the morning, tasteless at noon, and bitter in the even- 
ing. The formation of acids is effected during the night by a true 
process of oxidation: these are deprived of their acid properties 



ACTION OF LEAVES. 43 

is in proportion to the intensity of the light which 
strikes a leaf, the smallest amount being in shady 
places ; and the healthiness of a plant is, cceteris pari- 
bus, in proportion to the quantity of carbonic acid 
decomposed ; therefore, the healthiness of a plant 

during the day and evening, and are changed, by the separation of 
a part of their oxygen, into compounds containing oxygen and 
hydrogen either in the same proportions as in water, or even with 
an excess of hydrogen, which is the composition of all tasteless and 

bitter substances Most vegetable physiologist* have 

connected the emission of carbonic acid during the night with the 
absorption of oxygen from the atmosphere ; and have considered 
these actions as a true process of respiration in plants, similar t«j that 
of animals, and, like it, having for its result the separation of carbon 
from some of their constituents. This opinion has a very weak and 
unstable foundation. The carbonic acid, which has been absorbed 
by the leaves and by the roots, together with water, ceases to be 
decomposed on the departure of daylight It is dissolved in the 
juices which pervade all parts of the plant, and escapes every mo- 
ment through the leaves, in quantity corresponding to the water 

which evaporates Plants during their life constantly 

possess the poAver of absorbing by their roots, moisture, and, along 
with it, air and carbonic acid. Is it, therefore, surprising that the 
carbonic acid should be returned unchanged to the atmosphere, 
along with water, when light (the cause of the fixation of its carbon) 
is absent ? Neither this emission of carbonic acid nor the absorption 
of oxygen has any connexion with the process of assimilation ; nor 
have they the slightest relation to one another ; the one is a purely 
mechanical, the other a purely chemical process. A cotton wick, 
enclosed in a lamp which contains a liquid saturated with carbonic 
acid, acts exactly in the same manner as a living plant in the night. 
"Water and carbonic acid are sucked up by capillary attraction, and 
both evaporate from the exterior part of the wick." Ziebig, Organic 
Chemistry in its applications to Agriculture and Physiology, (London, 
1840,) pp. 27 — 33, passim; a work which comprises a masterly view 
of the chemical phenomena of vegetation. G.J 



44 VITAL ACTI0X3. 

should be in proportion to the quantity of light it 
receives by day. 

68. But, while this is true as a general axiom, it is 
necessary to observe that some plants are naturally 
inhabitants of shady situations, and are so organised 
as to be fit for such places and for no others : plants 
of this description will not endure full exposure to the 
sun ; not because an abundant decomposition of car- 
bonic acid is otherwise than favourable to them, but 
because their epidermis allows the escape of water 
too freely by insensible perspiration, under the solar 
stimulus. 

69. The mere fact of plants absorbing fluids from 
the earth, would render it probable that they have 
some means of parting with a portion of it by their 
surface ; but that they do perspire is susceptible of 
direct proof, and is by no means a mere matter of 
inference. 

70. We do not indeed see vapour flying off from 
the surface of plants ; neither do we from that of ani- 
mals, except when the air is so cold as to condense 
the vapour ; yet we know that in both cases perspira- 
tion is perpetually going on, and it would appear that 
in plants it takes place more abundantly than in ani- 
mals. If a plant covered with leaves is placed under 
a glass vessel, and exposed to the sun, the sides of the 
vessel are speedily covered with dew, produced by 
the condensation of the insensible perspiration of the 
plant. If the branch of a plant is placed in a bottle 
of water, and the neck of the bottle is luted to the 
branch, so that no evaporation can take place, never- 



ACTION OF LEAVES. 



45 



theless the water will disappear ; and this can only 
happen from its having been abstracted by the branch 
which lost it again by insensible perspiration. Hales, 
an excellent observer, devised many experiments 




46 VITAL ACTIONS. 

connected with, this subject ;* among others the fol- 
lowing, which he relates thus : — " August 13. In the 
very dry year 1723, I dug down 2h feet deep to the 
root of a thriving baking pear tree, and laying bare 
a root half an inch in diameter (fig. 7) I cut off the 
end of the root at i, and put the remaining stump 
(i n) into the glass tube d r, which was an inch in 
diameter, and eight inches long, cementing it fast at 
r; the lower part of the tube dz was eighteen inches 
long and a quarter of an inch diameter in bore. . . . 
Then I turned the lower end of the tube (z) upper- 
most, and filled it full of water, and then immediately 
immersed the small end z into the cistern of mercury 
at the bottom, taking away my finger which stopped 

up the end of the tube z The root imbibed 

the water with so much vigour, that in six minutes' 
time the mercury was raised up the tube d z as high 

as 2, namely, eight inches The next morning 

at eight o'clock the mercury was fallen to two inches 
in height, and two inches at the end of the root i were 
yet immersed in water. As the root imbibed the 
water, innumerable air bubbles issued out at \ which 
occupied the upper part of the tube at r as the water 
left it." On another occasion he planted a sunflower 
3 5 feet high in a garden pot, which he covered with 
thin milled lead, cementing all the joints so that no 
vapour could escape except through the sides of the 
pot and through the plant itself; but providing an 
aperture capable of being stopped, through which the 

* See Vegetable Statics, London, 1727. 



ACTION OF LEAVES. 47 

earth in the pot could be watered. After fifteen days, 
viz., from July 3 to August 8, he found, upon making 
all necessary allowances for waste, that this sunflower 
plant 3 2 feet high, with a surface of 5616 square 
inches above the ground, had perspired as follows: — 

Ounces 
Avoirdupois. 

In twelve hours of a very dry warm day . 30, 

On another day 20, 

In a dry warm night without dew ... 3, 
In a night with some small dew . . . ; 
and that when the dew was copious, or there was 
rain during the night, the plant and pot were 
increased in weight two or three ounces. Other per- 
sons have instituted other experiments of a similar 
nature, the result of all which is, that the insensible 
perspiration of plants is very considerable,* Hales 

* The amount of this force is strikingly illustrated by the fol- 
lowing circumstances recorded by the late Mr. Braddick. " One 
experiment I will mention, as it may serve to show the great power 
of the rising sap in the vine, while its buds are breaking. On the 
20th of March, in the middle of a warm day, I selected a strong 
seedling vine five years old, which greAV in a well prepared soil, 
against a south-west wall; I took off its head horizontally with 
a clean cut, and immediately observed the sap rising rapidly 
through all the pores of the wood, from the centre to the bark. I 
wiped away the exuded moisture, and covered the wound with a 
piece of bladder, which I securely fastened with cement, and a 
strong binding of waxed twine. The bladder, although first drawn 
very close to the top of the shoot, soon began to stretch, and to rise 
like a ball over the wound ; thus distended, and filled with the sap 
of the vine, it felt as hard as a cricket ball ; and seemed to all 
appearance, as if it would burst. I caused cold water from a well 



48 VITAL ACTIONS. 

says his sunflower perspired seventeen times more 
than a man. There is, however, this important 
peculiarity in vegetable perspiration, that it takes 
place only or principally in sunlight. The last expe- 
riment shows that, while the sunflower was losing 
from twenty to thirty ounces of water daily during 
the day, it lost only three ounces during the night 
without dew, and that there was no loss whatever if 
a slight dew were present. Here it is probable that 
the small amount which was lost at night was parted 
with by the sides of the garden pot, and that the 
plant itself lost nothing ; for it is in evidence that the 
perspiration of plants is in proportion to the quantity 
of sunlight that strikes them, and that in darkness 
they perspire little or not at all.* It is no doubt 
true, that in a dry atmosphere plants will lose their 
water day and night ; but it is equally certain that 
under such circumstances they will lose very much 
more by day than by night. They will, however, 
lose much more by day in a dry atmosphere in a 
given time, than they will in an atmosphere abound- 
ing in moisture. 

to be thrown on the roots of the plant ; bnt neither this nor any 
other plan that I could devise, prevented the sap from flowing, 
which it continued to do with so much force as to burst the bladder 
in about forty-eight hours after the operation was performed; the 
weather continuing the whole time warm and gonial. — (Sort Trans., 
v. 202.) 

* M. De Candolle distinguishes between exhalaison or perspira- 
tion, which is a vital action, deperdition or evaporation, which is 
merely physical. But the latter is too s nail in amount to be worth 
taking into account for practical purpose-. 



ACTION OF LEAVES. 49 

71. Although perspiration thus appears to be prin- 
cipally excited by the solar rays, and to be in a given 
plant in proportion to their intensity, yet we are not 
authorised in concluding that perspiration is not 
increased or diminished by the medium in which a 
plant grows. Immersed in water, perspiration is 
necessarily arrested ; in an ordinary atmosphere, 
it will be in proportion to the quantity of elastic 
vapour the atmosphere may contain ; and it is proba- 
ble, although there are no experiments upon the sub- 
ject, that it is increased in proportion to the rare- 
faction of the air. 

72. Since a plant does not perspire at night, and 
since its absorbing points, the roots, remain during 
that period in contact with the same humid medium 
as during the day, they will attract fluid into the 
system of the plant during the night, and, conse- 
quently, the weight of the individual will be increased, 
as Hales found to be the case. In like manner, 
if plants in the shade are abundantly supplied with 
moisture at the roots, they also will gain more than 
they can lose ; and, as this will be a constant action, 
the result must necessarily be to render all their 
parts soft and watery. 

73. It is evident, from what has been stated, that 
leaves must derive the food they digest from the 
earth through the medium of the roots; and that 
they, while alive, maintain a kind of perpetual suck- 
ing action upon the stem, which is communicated to 
the spongelets. That this must be of a very powerful 
nature is apparent from the fact, that the smallest 

3 



50 VITAL ACTIONS. 

leaf at the extremity of the branch of a lofty tree 
must assist in setting in action the absorbing power 
of roots, at a distance equal, perhaps, to three thou- 
sand times its own length. If this reciprocal action 
is not maintained without interruption, and if any- 
thing occurs to check it during the period of vegeta- 
tion, the plant will suffer in proportion to the amount 
of interruption. For example, if the roots are placed 
in a warmer medium than the branches, and are 
thus induced to absorb fluid faster than the slower 
action of the leaves can consume it, the superfluous 
sap will burst through the stem and distend its tissue 
till the excitability is impaired or destroyed. Or if, 
on the other hand, a branch is caused to grow in 
a warm medium, while the roots remain in a very 
cold medium, the former will consume the liquid sap 
faster than the latter can supply it, and the con- 
sequence will be, that the leaves will die, or the fruit 
will fall off, or the flowers be unable to set their 
fruit, from want of a constant and sufficient supply 
of food. Not that it is necessary for the temperature 
of the earth and air to be equal, for this does not 
happen in nature ; but it is requisite that they should 
have some near relation to each other. 

74. It is generally, however, believed, that leaves 
absorb fluid from the air ; and their stomates appear 
well adapted for that purpose, by their position in 
most abundance on the under side of leaves ; and 
the possibility of recovering drooping or sickly plants, 
by syringing their epidermis copiously, seems to ren- 



ACTION OF LEAVES. 51 

der this fact almost certain." It is, however, thought 
by some, that leaves have no power of absorbing 
water, even in an elastic state ; and that the renova- 
tion of plants by syringing is owing to a diminution 
of perspiration. 

75. It is to the action of leaves, — to the decompo- 
sition of their carbonic acid, and of their water; 
to the separation of the aqueous particles of the sap 

* Mr. Knight entertained the opinion, that water is sometimes 
absorbed by leaves to such an extent as to cause a descent of the 
sap through the alburnum; a derangement of function to which lie 
even ascribed the attacks of mildew fungi upon plants. The secon- 
dary and immediate causes, he says, of this disease, and of its con- 
geners, " have long appeared to me to be the want of a sufficient 
supply of moisture from the soil, with excess of humidity in the air, 
particularly if the plants be exposed to a temperature below that 
to which they have been accustomed. If damp and cold weather 
in July succeed that which has been warm and bright, without the 
intervention of sufficient rain to moisten the ground to some depth, 
the wheat crop is generally much injured by mildew. 1 suspect 
that in such cases an injurious absorption of moisture, by the leaves 
and stems of the wheat plants, takes place : and I have proved that 
under similar circumstances much water will be absorbed by the 
leaves of trees, and carried downwards through their alburnous 
substance; though it is certainly through this substance that the 
sap rises, under other circumstances. If a branch be taken from a 
tree when its leaves are mature, and one leaf be kept constantly 
wet, that leaf will absorb moisture, and supply another leaf below 
it upon the branch, even though all communication between them 
through the bark be intersected ; and, if a similar absorption takes 
place in the straws of wheat, or the stems of other plants, and 
a retrograde motion of the fluids be produced, I conceive that the 
ascent of the true sap or organisable matter into the seed-vessels 
must be retarded, and that it may become the food of the parasitical 
plants, which then only may grow luxuriant and injurious."— 
(Hort. Trans., i. 86.) 



52 VITAL ACTIONS. 

from the solid parts that were dissolved in it ; to the 
deposition thus effected of various earthy and other 
substances, either introduced into plants, as silex and 
metallic salts, or formed there, as the vegetable alka- 
loids ; to the extrication of nitrogen ; and, probably, 
to other causes as yet unknown, — that the formation 
of the peculiar secretions of plants, of whatever kind, 
is owing. And this is brought about principally, 
if not exclusively, by the agency of light. Their 
green colour becomes intense, in proportion to their 
exposure to light within certain limits, and feeble, in 
proportion to their removal from it ; till, in total and 
continued darkness, they are entirely destitute of 
green secretion, and become blanched or etiolated. 
The same result attends all their other secretions ; tim- 
ber, gum, sugar, acids, starch, oil, resins, odours, fla- 
vours, and all the numberless narcotic, acrid, aromatic, 
pungent, astringent, and other principles derived 
from the vegetable kingdom, are equally influenced, 
as to quantity and quality, by the amount of light to 
which the plants producing them have been exposed. 
76. It is, however, to be observed that, as has 
already been stated (68), the capability of plants to 
bear the action of direct light varies according to 
their specific nature. One species is organised to suit 
the atmosphere of a dense wood, into which diffuse 
light only will penetrate ; another is planted by nature 
on the exposed face of a sunburnt rock, upon which 
the rays of a shadeless sun are daily striking ; in 
these cases, the light which is necessary to the one 
would be destructive of the other. The organic dif- 



ACTION OF LEAVES. 53 

ference of such species seems to consist chiefly in the 
epidermis, which regulates the amount of perspi- 
ration (61). It is therefore to be remarked, that it is 
not the greatest quantity of light which can be 
obtained that is most favourable to the healthiness of 
plants, but the greatest quantity they will bear with- 
out injury. If the former were true, the concentrated 
light of a lens would be better than the strongest 
ordinary light ; but the effect of the concentrated 
light of a lens is to burn the surface, and the ordi- 
nary solar rays produce the same effect upon many 
plants, probably by exhausting the tissue of its water 
faster than it can be supplied from the roots. 

77. In the course of time, a leaf becomes incapable 
of performing its functions ; its passages are choked 
up by the deposit of sedimentary matter ; there is no 
longer a free communication between its parenchyma 
and that of the rind, or between its veins and the 
wood and liber. It changes colour, ceases to decom- 
pose carbonic acid, absorbs oxygen instead, gets into 
a morbid condition, and dies : it is then thrown off. 
This phenomenon, which we call the fall of the leaf is 
going on the whole year round, except mid-winter, 
in some plant or other. Those which lose the whole 
of their leaves at the approach of winter, and are 
called deciduous, begin, in fact, to cast their leaves 
within a few weeks after the commencement of their 
vernal growth ; but the mass of their foliage is not 
rejected till late in the season. Those, on the other 
hand, which are named evergreens, part with their 
leaves much more slowly; retain them in health 



54 VITAL ACTIONS. 

at the time when the leaves of other plants are perish- 
ing ; and do not cast them till a new spring has com- 
menced, when other trees are leafing, or even later. 
In the latter class, the functions of the leaves are 
going on during all the winter, although languidly ; 
they are constantly attracting sap from the earth 
through the spongelets, and are, therefore, in a state 
of slow but continual winter growth. It usually hap- 
pens that the perspiratory organs of these plants are 
less active than in deciduous species. 

78. In general, a leaf is an organ of digestion and 
respiration, and nothing more ; some leaves have, 
however, the power of forming leaf-buds, if placed in 
or upon earth, under suitable circumstances. The 
Bryophyllum calcinum forms buds at the indenta- 
tions of its margin; Malaxis paludosa throws off 
young buds from its margin ; Tellima grandiflora 
occasionally buds at the margins of its leaves : the 
same thing happens to many Ferns ; and several 
other cases are known. 



MOTION CI FLOWERS. DO 

CHAPTER V, 

ACTION OF FLOWERS. 

Structure of Flowers. — Karnes of their Paris. — Ten- 
dency of the Parts to alter and change into each other, 
and into Leaves. — Double Flowers. — Analogy of 
Flowers to Branches. — Cause of the Production of 
Flowers. — Of Productiveness. — - Of Sterility. — Uses of 
the Parts of a Floicer. — Fertilization^ — Hybrids. — 
Crossbreeds. 

79. A Flower is that part of a plant which is 
formed for the purpose of reproducing the species 
by means of seeds. It consists of floral envelopes 
and sexes. 

80. The floral envelopes are : 1. the calyx, which 
is usually green, and always the most external ; and, 
2. the corolla, which is commonly thin, gaily coloured, 
more fugitive than the calyx, and placed next within 
it ; each of these consists of leaves, called sepals in the 
calyx, and petals in the corolla. Both calyx and 
corolla are usually present ; but in some cases only 
one envelope is formed, as in the Marvel of Peru ; and 
in other cases the flower has no envelopes, as in the 
Willow. Envelopes are, therefore, not a necessary 
part of a flower. 

81- In the middle of the flower stand the sexes, 



56 



TITAL ACTIONS, 



called stamens and pistil, of which the pistil occupies 
the centre, and the stamens surround it ; except in 
those cases where the sexes are produced in separate 
flowers, when each sex is central in its own flower. 
The stamens consist of a filament and an anther, in 
the inside of the latter of which is secreted a powdery 
substance called pollen. The pistil consists of ovary, 
style, and stigma, in the inside of the first of which 
are ovules or .young seeds. 

82. Although the floral envelopes may be, and often 
are, absent, wholly or in 
part, yet the sexes are al 
ways present. Consequen t- 
ly the latter are all that is 
essential to a flower, and 
no part can be a flower 
from which they are ab- 
sent. 

83. Notwithstanding the 
difference in form and of- 
fice of the parts of a flow- 
er, they have evidently a 
strong tendency, in cul- 
tivated plants, to change 
into or assume the appear- 
ance of each other. In the 
Poppy, the Garden Ane- 
mone, and many others, 
the stamens change into 
petals; in the Anemone, the Ranunculus, &c, the 
pistil changes into petals ; in the Primrose, Cowslip, 




ACTION OF FLOWERS. 



57 



&c, the calyx changes into petals ; in the Houseleek, 
the stamens become pistils ; and so on. Hence the 
origin of double flowers. In a double Barbadoes 
Lily, described by me in the Transactions of the Hor- 
ticultural Society, in which the parts were very much 
confused, the young seeds were borne by the edges 
of the stamen-like petals, {fig. 8.) 

84. In their ordinary state the parts of a flower are 
extremely unlike leaves, and each has its allotted 
office, which is not the office of a leaf; they are also 
incapable of forming leaf : buds in their axils. But, 
although such is the case, there is found a strong and 




general tendency on the parts of both the floral 
envelopes and sexes to change to leaves, like the 
leaves of the stem. In the white clover (Trifolium 
repens, fig. 9), all the parts often become leaves ; in 
the Fraxinella ( fig. 10), this has also been remarked j* 

* ^Proceedings of the Horticultural Society, vol. i. p. 37. 



58 



VITAL ACTIONS. 




so has it in the Nasturtium, in Sieversia montana, and 
many other instances. A 
partial alteration into leaves 
is of very frequent occur- 
rence in the parts of a flower. 
In the Eose ; the sepals arid 
pistil are frequently changed 
into leaves ; in the Double 
Cherry, the pistil is almost 
always to be found in the 
form of a leaf; and books 
on structural botany abound 
in the records of similar 
cases. It sometimes happens that buds are not only 
formed, but developed, at the axils of the parts of a 
flower, as in a Celastrus scandens observed by Kunth, 
{fig. 11.) In the Pear, it is 
not uncommon to find two or 
three small pears growing out 
of an older one {fig. 12), each 
of which pears may be traced 
to the axil of some one of the 
parts of the flower ; and rose* ^ 

buds are frequently seen growing oat of Eose.<. A 
very striking and uncommon case of this sort was 
observed by the late Mr. Knight in the Potato (fig. 
13), whose flowers produced young potatoes in the 
axils of the sepals and petals.* Occasionally, the 
centre of a flower lengthens and bears its parts upon 
its sides, as in the Pear and Apple, whose fruit is 




Proceedings of the Horticultural Society, vol. '. }>. 39, fig. -• 



ACTION OF FLOWERS. 
12 



39 




often found in the state of a short branch. Still more 
rarely a flower lengthens, and produces from the axils 






v % 



of its parts other flowers arranged over its sides, as m 
the Double Pine-apple of the Indian Archipelago. 
The following very striking illustrations of the^e facts 
have, among many others, occurred in the present 
season (1839). Fig. 14: represents a branch of a Pear, 
in which one flower (a) is in a deformed state, but 



00 



VITAL ACTIONS, 




still sufficiently recognisable, and another completely 
changed into a branch ; the calyx assuming the 
appearance of leaves or leafy scales (s s), the petals 



ACTION OF FLOWERS. 61 

also partially transformed into leaves (p p), while the 
whole apparatus of stamens and pistils is converted 
into an ordinary branch. Fig. 15 shows the state of 




plants of Potentilla nepalensis with their flowers 
changing to branches : a is a flower in the ordinary 



62 VITAL ACTIONS. 

condition ; at 6 it is partly changed in a slight degree ; 
at c all the sepals, petals, and stamens are converted into 
leaves, bnt the pistils are little changed ; at d the 
sepals, petals, and stamens are but little altered, but 
the receptacle of the fruit is lengthening into a branch, 
and is covered by the carpels partly converted into 
leaves, and some of them near the apex producing 
flowers from their axils ; finally, at e, the whole of 
the floral apparatus is changed into a rosette of leaves. 
It therefore appears, that although the parts of a 
flower are different both in appearance and office 
from leaves, yet that they do all assume, under parti- 
cular circumstances, the same appearance and office. 
Hence it is inferred that they are really nothing more 
than leaves in a modified state ; and, consequent^, 
that a flower is a very short branch, and a flower-bud 
analogous in many respects to a leaf-bud. A leaf-bud 
is a collection of leaf-scales of the same or similar 
form, arranged round a central very short branch, 
having a growing point. A flower-bud is a collection 
of leaf-scales of different forms, arranged round a 
central very short branch, not having a growing point 
under ordinary circumstances. In this latter respect 
it resembles those buds of the Larch which form 
leaves in starry clusters, without extending into a 
branch. Many points in horticulture could not be 
explained until the existence of this analogy was 
made out."* 

* [This doctrine has been taught at different time?, by different 
independent observers. Among other persons, I find that Mr. Knight 
had come to tie same conclusion, at a time when the views of 



ACTION OF FLOWERS. 63 

85. What it is that causes a plant to convert some 
of its buds into flowers, by fashioning the leaves into 
calyx, corolla, stamens, and pistils, while other buds 
become branches clothed with ordinary leaves, is be- 
yond the reach of explanation. There are, however, 
some facts connected with it which require notice. It 
is clear that plants begin to fructify at some determin- 
ate period, varying in different species. In annuals 
this occurs in a few weeks or months after germina- 
tion ; in biennials a longer period is required before 
this condition is arrived at ; and in shrubs and trees 
a still greater age must be acquired. The American 
Aloe will not flower before it is thirty years old, under 



Wolffius and Goethe were quite unknown in England. He says: 
"The buds of fruit trees which produce blossoms, and those which 
afford leaves only, in the spring, do not at all differ from each other, 
in their first stage of organisation, as buds. Each contain the rudi- 
ment of leaves only, which are subsequently transformed into the 
component parts of the blossom, and in some species of the fruit also. 
I have repeatedly ascertained that a blossom of a Pear or Apple tree 
contains parts which previously existed as the rudiments of five 
leaves, the points of which subsequently form the five segments of 
the calyx ; and I have often succeeded in obtaining every gradation 
of monstrosity of form, from five congregated leaves (that is, five 
leaves united circularly upon an imperfect fruit-stalk) to the perfect 
blossom of the Pear tree. The calyx of the Rose, in some varieties, 
presents nearly the perfect leaves of the plant, and the large and 
long leaves of the Medlar appear to account for the length of the 
segments, in the empalement of its blossom. The calyx of the blos- 
som of the Plum and Peach tree is formed precisely as in the pre- 
ceding cases, except that the leaves which are transmuted into the 
calyx separate at the base of the fruit, and become deciduous, instead 
of passing through and remaining a component part of it." (Trans- 
actions of ike Horticultural Society, vol. ii. p. 364. May 6, 1817.) 



64 VITAL ACTIONS. 

the most favourable conditions ; and under unfavour- 
able circumstances, the age at which it fructifies is so 
much increased as to have given rise to the vulgar 
belief that it flowers only after a hundred years. This 
very curious subject has been little investigated, and 
we have no comparative statements of the ages at 
which different species begin to bear ; but the fact is 
certain. It is often, however, in the power of man to 
advance or retard these periods artificially. "What- 
ever produces excessive vigour in plants is favour- 
able to the formation of leaf-buds, and unfavourable 
to the production of flower-buds ; while, on the other 
hand, such circumstances as tend to diminish luxu- 
riance, and to check rapid vegetation, without affect- 
ing the health of the individual, are more favourable 
to the production of flower-buds than of leaf-buds. 
Thus, a plant in a sterile soil and exposed situation 
flowers sooner and more abundantly than one in a 
rich and shaded place ; young vigorous plants flower 
later and less abundantly than old ones. In India 
and China, fruit trees are made to bear by cutting 
their roots, or exposing them periodically to dryness ; 
and in this country the same practice is observed, es- 
pecially with the fig-tree. An apparent exception to 
this law is found in the fact that a seedling fruit tree 
may be made, by grafting upon any old stock, to bear 
flowers at an earlier age than it otherwise would have 
done ; for the effect of grafting it thus is certainly not 
to render it less vigorous, but the contrary. But it 
is probable that all these facts arise out of one com- 
mon law, which is, that the period when a plant be- 



actio:; of flowers. 65 

gins to flower depends upon the presence in its sys- 
tem of a sufficient quantity of secreted matter fit for 
the maintenance of the flowers when produced. Un- 
der ordinary circumstances, a considerable part of all 
the nutritious secretions elaborated by the leaves are 
expended in the production of new leaves ; but, after 
a time, a greater supply is formed than the leaves re- 
quire, and the residue collects in the system ; as soon 
as the residue has arrived at the necessary amount, 
flowers may begin to form. If the sterile branch of a 
tree is ringed,* it ceases to be sterile ; and this can 
only be accounted for upon the supposition that the 
secreted matter of the branch, instead of being con- 
veyed away into the trunk and roots, is stopped by 
the annular incision, above which it is compelled to 
accumulate. If a tree that is unproductive be trans- 
planted, it begins to bear ; in this case the operation 
injures its roots ; sap is therefore less abundantly sup- 
plied in the succeeding season to the leaves ; the 
leaves are therefore less able to grow than they pre- 
viously were, and they consequently do not consume 
the nutritious matter lying in the branches, and which 

* One of the effects of ringing has been observed to consist in the 
formation of numerous barren shoots below the wound, while fertile 
shoots appear above it. This is conformable to the theory of the 
formation of flowers being determined by a superabundance of 
nutritious matter in a given place. The bark below the annular 
excision is cut off from a supply of the sap elaborated by the leaves 
above it; and, at the same time, in consequence of the obstruction 
of the wound to the ascent of the crude sap, an unusual supply of 
the latter is forced towards the buds in the bark below the wound; 
which buds, being chiefly fed with crude sap, push forth into 
branches and leaves, but bear no flowers. 



66 VITAL ACTIONS. 

the j would have expended, had they been able to 
grow with their former vigour ; hence the nutritious 
matter accumulates, and flower-buds are formed. In 
this country, if a fruit tree has its crop destroyed one 
year, it bears the more abundantly the next ;* owing, 
no doubt, to the accumulation in its system of that 
nutritious matter which would not have been present 
there, had the crop which was destroyed, been allow- 
ed to grow : and the reverse of this is well known to 
be the fact ; an excessive crop one year being follow- 
ed by a scanty crop the succeeding } T ear. So, when 
a young seedling fruit tree is made to bear prema- 



* The " bearing year" of the apple orchards, all over this country, 
is a well known popular illustration of this remark. This arises 
simply from the tendency in the apple, when left to itself, to bear 
such large crops one year, as to require the next year to recover 
sufficient strength to bear again. This becomes a kind of fixed 
constitutional habit in a given variety, and is continued by grafting, 
so that whole orchards bear one year, and are unfruitful the next> 
with great regularity. On the other hand, certain sorts, like the 
Bellflower and Holland pippin, which bear but moderate crops, in 
strong soils bear every year. A. J. D. 

The habit itself may be corrected or changed, when the tree or 
orchard is young, by picking off all the fruit that sets the first year 
the tree bears a good crop, and thus forcing it to take its bearing 
year the next season. In parts of the country where the " apple 
year" is pretty uniformly the same in all the orchards, we have known 
clever orchardists to increase their profits by thus inducing their 
young orchards to take the barren year of the country around for their 
fruitful one, and the habit once formed the tree will continue it. In 
a garden where the cost of labor is not so much an object, apple trees 
may have half their fruit regularly thinned-off when they are as 
large as bullets, by which process the tree will not exhaust itself, 
and will bear a moderate crop the next year. A J. D. 



ACTION OF FLOWERS. 67 

turely by grafting it upon an old stock, the effect of 
which will apparently not be to diminish its vigour, 
it may be conceived that, in the first place, the seed- 
ling will receive a considerable quantity of nutritious 
matter from the old stock, where it has been already 
collected, and that thus the supply will be greater 
than the consumption, however large the latter may 
be ; and, secondly, that, at the time of union of itself 
with the stock, there will be sufficient interruption of 
continuity in the bark to oppose some obstacle to the 
descent from the seedling of whatever matter it may 
have received or formed. Hence, it is an axiom in 
vegetable physiology, that the production of flower- 
buds depends upon the presence of nutritious matter 
in sufficient abundance for their support. 

86. The use of the calyx and corolla is too uncer- 
tain and unimportant to demand much notice. The 
calyx is usually regarded as a protecting organ, and 
the corolla as a part for the embellishment of the 
sexes. They neither appear to be of much physiolo- 
gical importance ; more especially the corolla, or it 
would not be absent in such large numbers of plants. 

87. The use of the stamens is to effect the fertilisa- 
tion of the young seed contained in the pistil. To 
this end, the pollen of the anther must be applied to 
the stigma ; the result of which is, that an embryo, 
the rudiment of a future plant, is generated in the 
inside of the young seed, and, when mature, is capa- 
ble of multiplying the species. It is, however, to be 
observed that the seed, when ripe, will not renew the 
species from which it is derived, with all its indi- 



68 VITAL ACTIONS. 

vidual peculiarities ; the seed of a Green Gage Plum, 
for instance, will not, with any certainty, produce a 
plant having the sweet green fruit of that variety, 
but it may produce a plum whose fruit is red and 
acid. All that the seed will certainly do is to pro- 
duce a new individual of the plum species ; the pecu- 
liarities of individuals are perpetuated by other 
means, and especially by leaf-buds. (See Book II.) 

88. If the pistil of one species be fertilised by the 
pollen of another species, which may take place in the 
same genus, or if two distinct varieties of the same 
species be in like manner intermixed, the seed which 
results from the operation will be intermediate be- 
tween its parents, partaking of the qualities of both 
father and mother. In the first case the progeny is 
hybrvl., or mule ; in the second, it is simply crossbred. 

89. In general, crossbreds are capable of producing 
fertile seed, and thus of perpetuating one of the spe- 
cies from which they sprang. Hybrids, on the con- 
trary, are often sterile, and therefore incapable of 
yielding seed. 

90. Reasoning -from a few facts, and from the ana- 
logy of the higher orders in the animal kingdom, it 
has been believed that all vegetable hybrids are 
sterile ; and, when sterility is not the consequence 
of the intermixture of two species, it has been thought 
that such species are not naturally distinct, however 
different their appearance. But facts prove that 
undoubted hybrids may be fertile ; and when we 
consider that plants are not analogous to the higher 
orders of animals, but to the lowest, concerning 



MATURATION OF THE FRUIT. 6^ 

whose habits we know nothing whatever, it is obvious 
that no analogical inferences can be safely estab- 
lished. 



CHAPTEE VI. 

OF THE MATURATION OF THE FRUIT. 

Changes it undergoes. — Superior and inferior Fruit. 
— Is fed by Branches upon organisable Matter fur- 
nished by Leaves. — Physiological Use of the Fruit. — 
Nature of Secretions. — The Clianges they undergo. — 
Effect of Heat— Of Sunlight— Of Water.— Seeds. 
Origin of their Food. — Cause of their Longevity. — Of 
their Destruction. — Difference in their Vigour. 

91. After the fertilisation of the seed has taken 
effect, the pistil by itself, or the pistil and surround- 
ing parts, go on growing ; alter their appearance, as 
well as size ; acquire new qualities of colour, texture, 
flavour, &c. ; and become the fruit. There are two 
kinds of fruit essentially very different ; in some 
instances, the pistil grows separately from the floral 
envelopes, which drop off, and the fruit is formed by 
an enlargement and alteration of the sides of the 
pistil only ; it is then called superior : in other 
instances, the pistil and floral envelopes all grow 
together, and the fruit consists of an enlargement and 



70 VITAL ACTIONS. 

alteration of the whole flower ; it is then said to be 
inferior. There is this essential difference between 
the two, — that the superior fruit adheres to the branch 
bj the base of the pistil alone ; while the attachment 
of the inferior fruit is secured by the base, not only 
of the pistil, but of all the floral envelopes surround- 
ing it. A Peach is a superior fruit ; an apple infe- 
rior. 

92. A flower being a kind of branch, as has been 
already shown, and the fruit being an advanced stage 
of a flower, it follows that a fruit is also a kind 
of branch. It has originally the same kind of organic 
connexion with the plant as other branches, and, like 
them, requires to be supplied with food, in the absence 
of which it perishes or languishes. Nevertheless, as 
its leaves have in but a slight degree the power 
of forming secretions, and consequently of producing 
woody tissue in its interior, it will soon drop off its 
parent, unless the supply of food to it be copious, 
and its healthy condition permanently secured. Now, 
as the supply of food to the plant is determined by 
the attracting force of the leaves of which it consists, 
and as a superior fruit consists of a smaller number 
of leaves than an inferior fruit, it follows that the 
attracting power of an inferior fruit is, cceteris paribus, 
greater than that of a superior, and consequently the 
former is less likely to drop off; and as the pistil of 
a superior fruit, being unprotected, is more exposed 
to external influences, such as that of frost, or a cold 
dry atmosphere, than an inferior, it also follows that 
the latter is less liable to suffer from such causes, as 



MATURATION OF THE FRUIT. 71 

compared with, a superior fruit of similar constitu- 
tional power. * 

93. It is, however, to be remarked that these rules 
may be interfered with by special causes ; as in the 
case of the Fig, where the superior fruit is seated on 
an enlarged receptacle, which acts as if it were a 
large surface of leaves adhering to the pistil. 

94. It may be conceived that, as the fruit is an 
altered state of a leaf, its physiological action will 
resemble that of a leaf, in proportion as it retains its 
organic similitude ; and this is found to happen, a fruit 
decomposing carbonic acid, &c, under the influence 
of light, so long as it retains its original green folia- 
ceous character. In the Pea, for example, whose pod 
is green until it begins to die, the action is always 
similar to that of a leaf: but in the Peach, whose tex- 
ture becomes pulpy, and unlike that of a leaf, the 
physiological action eventually ceases to be exactly 
that of the latter organ. 

95. But although a fruit has, like a leaf, the power 
of forming secretions by elaborating the sap which is 

* The following table shows which of our commonly cultivated 
plants hare superior or inferior fruits: — 

Stiperio?\ Inferior. 

Strawberry. Apple. 

Raspberry, Pear. 

Peach. Quince. 

Plum, etc. Medlar. 

Apricot. Currant. 

Cherry. Gooseberry. 

Grape. Melon. 

Fig. Cueumber, 



72 VITAL ACTIONS. 

attracted into it, yet, because of its smallness, the 
amount of this power is inconsiderable ; it contributes 
little to the general secretions of the plant that bears 
it, but expends its powers in the elaboration of matter 
for its own use. That it does, however, form wood, 
like ordinary leaves, is evident, if the flower-stalk of 
a Cherry is compared with the stalk of the fruit of the 
same tree ; and this becomes still more apparent when 
the elaborating forces of many separate fruits are, in 
consequence of their compact arrangement, brought 
to contribute to the ligniiication of a common stalk, 
as iD the Pinaster tree. 

96. The great purpose for which the fruit is formed 
seems to be the protection and nutrition of the seed, 
the perfect maturation of which is essential to the per- 
petuation of the races of plants. In most cases the 
whole of the fluid or nutritious parts is consumed in 
effecting this end ; but in certain instances there is a 
surplus, which, if sweet, and unmixed with delete- 
rious secretions, becomes fit for food. In either case, 
the fruit has, in common with leaves, the power of 
attracting food from the surrounding parts; and we 
see that this property causes the destruction of some 
fruits by their neighbours which are more advanced 
in growth, or accidentally more vigorous, and whose 
attracting power is so great as to draw to themselves 
all the food intended for the weaker fruits, which then 
fall off. Of the food thus to be consumed in the ma- 
turation of the fruit, a portion is derived from the 
atmosphere, but the principal part has to be prepared 
by the leaves, which obtain it from the earth through 



MATURATION OF THE FRUIT. 73 

the roots. It is, therefore, evident, that all causes, of 
whatever nature, which interfere with the healthy 
and regular action of leaves and roots, will also inter- 
fere with the fruit. Or, if the leaves are placed in 
such a manner with respect to the fruit, or at so great 
a distance from it, that the fruit is unable to attract 
food from them, it must either suffer or perish. This 
explains why fruit formed upon naked branches will 
not continue to grow ; and why the presence of a leaf 
immediately above a fruit, on the same branch, is so 
beneficial to it. The size and excellence of fruit will 
hence be in proportion to the abundance of organisa- 
ble matter prepared and stored up in its vicinity.* 
97. Although fruit has, in common with leaves, 

* The accumulation of sap, and its consequent viscidity, may, 
however, he attended with disadvantage to a plant, as really hap- 
pens in the Potatoe, the most farinaceous varieties of which are 
liable to a disease called the "curl." Mr. Knight attributed this to 
the inspissated state of the sap, which, he conceived, if not suffi- 
ciently fluid, might stagnate in and close the fine vessels of the leaf 
during its growth and extension, and thus occasion the irregular 
contractions which constitute this disease. He therefore suffered 
a quantity of Potatoes, the produce almost wholly of diseased 
plants, to remain in the heap, where they had been preserved dur- 
ing winter, till each tuber had emitted shoots of three or four inches 
in length. These were then carefully detached, with their fibrous 
roots, from the tubers, and were committed to the soil, when, having 
little to subsist upon except water, not a single curled leaf was pro- 
duced, though more than nine tenths of the plants which these 
identical tubers subsequently produced were much diseased. The 
same effect has been produced by other persons, by taking up 
the tubers intended for seed before they were full grown, and con- 
sequently, before the excessive icspissation of their secretions had 
taken plaoa. 

4 



74 VITAL ACTIONS. 

the property of elaborating the sap, yet there is this 
difference between them ; tbat T while leaves return 
back into the stem what matters they form, fruit 
retains the principal part of what it forms for the use 
of itself or of the seeds it contains. This difference is 
probably to a considerable extent dependent upon 
the imperfect condition of the bark of the fruit-stalk, 
which has little power of carrying off from the fruit 
the matter which is formed within it. In those cases, 
however, in which the fruit has stomates, the aqueous 
particles are given off through the surface of the 
fruit, which then becomes hard or dry when ripe; 
but in others, in which there are no stomates, or very 
few, or very imperfect ones, the aqueous particles 
cannot be given off to any considerable amount, and 
the fruit becomes succulent. 

98. The maturation of the fruit is dependent, then, 
upon the action of the leaves and roots, and the secre- 
tions that it forms are principally derived from the 
former. Consequently, whatever contributes to the 
healthy condition of the leaves and roots will have a 
directly beneficial influence upon the fruit, and vice 
versa. It is, however, certain, that the juices fur- 
nished by the leaves undergo a further alteration by 
the vital forces of the fruit itself, which alteration 
varies according to species. Thus the fruit of the 
Peach is sweet, but there is no perceptible sweetness 
in its leaves ; and the fruit of the Fig is sweet and 
nutritious, while the leaves of that plant are acrid 
and deleterious. 

99. Among the immediate causes of the peculiar 



MATURATION OF THE FRUIT. 75 

changes that occur in the secretions of fruits, are heat 
and light ; without which the peculiar qualities of 
fruits are imperfectly formed, especially in species 
that are natives of countries enjoying a high summer 
temperature. It is found that among the effects of a 
high temperature and an exposure to bright light, is 
the production of sugar and of certain flavours ; and 
that under opposite circumstances, acidity prevails.* 
As sugar is more rich in carbon than vegetable acids, 
and has no free oxygen as they have, the sweetness 
of pulpy fruits ripened under bright sunshine may 
be understood to arise from the decomposition of 
carbonic gas, and the expulsion of oxygen, being 
greater under sunshine than in the shade. Another 
cause may be, the greater facility with which vegeta- 
ble acids enter into combination with gum and starch, 
and so form sugar, at a high than at a low tempera- 
ture.f 

100. One of the most essential of the alterations 

* [Fruits remain acid in cold summers: on the other hand, nearly 
all the trees of tropical climates produce oils, caoutchouc, and other 
substances which contain little or no oxygen. G.] 

f For Table of the Proportions of Carbon and Water in a few of 
the commonest Vegetable Secretions, ride next page. 

The gummy, mucilaginous, and gelatinous parts appear very sus- 
ceptible of changing into sugar ; thus M. Couverchel found that, if 
Apple jelly is treated with a vegetable acid dissolved in water, a 
sugar like that of Grape sugar is the result ; that the gum of Peas 
placed with oxalic acid in a temperature of 125°, is converted into 
sugar ; that the gum obtained from starch, mixed with the juice of 
green Grapes, renders it saccharine ; and, finally, that tartaric acid, 
assisted by heat, produces the same effect ; which is what causes 
most fruits to become sweet when cooked. {Be Candolle, Phys. Veg., 
p. 685. 



76 



VITAL ACTIONS. 



which occur in fruits during ripening, is the decom- 
position or dissipation of the water that thej attract 
from the stem. A diminished supply of water will, 
under equal circumstances, produce an accelerated 
maturation, because less time will be required to 
decompose or dissipate this element ; and, on the 
other hand, an excessive supply of water will retard 
or prevent ripening, in consequence of the longer 
time required for the same purpose. 



Table of the Proportions of Carbon and Water in a few of the 


commonest Vegetable Secretions. 








Water, 


Oxygen 


Substance. 


Carbon. 


or its 


in 






Elements. 


Excess. 


Gum (Berzelius) 


57-318 


42-682 




Starch (ditto) 


43-481 


56-518 




Tannin (ditto) 


51-160 


41-477 


3-568 


Sugar of Sugar-Cane (ditto) 


44-2 


55*79 




Grape Sugar (27i. de Saussure) 


86-71 


60-08 


341 


Lignine (Prout) 


50 


50 




Acid, Citric . 




. (Berzelius) 


41-309 


34-234 


24 -39^ 


Malic . 




. (Prout) 


40-68 


45-76 


13-56 


Oxalic . 




(ditto) 


19-04 


42-85 


38-11 


Tartaric 




. (ditto) 


32 


36 


32 


Ulmic . 




P. Boullay) 


56-7 


43-3 




Gallic . 




(Berzelius) 


56.64 


43-36 




Acetic . . 




(ditto) 


46-23 


53-17 






Hydrogen 








in Excess. 


Oil, Olive Th, de Saussure 


77-21 


10-71 


12-08 


of Almonds (Henry & \ 

Plisson) ) 


74-40 


13-37 


4-45 


of Anise (Th. de Saussure) 


83-468 


14-887 


6-465 


of LavendeT . (ditto) 


75-50 


14-59 


9-55 


of Roses . . (ditto) 


82*053 


■ 4.442 


12631 


of Turpentine ( Gay Lussac) 


88-348 


• • 


11-652 


Hydrocyanic Acid ( Gay Ltcssac ) 
& Thenard) \ 


44*39 




3-90 






(51-71 
titrofcen..) 


s 







MATURATION OF THE FRUIT. 77 

101. Seeds are affected by all circumstances that 
affect the fruit, which indeed, as has been already 
stated, appears to be created for their nutrition and 
preservation. In general, the fruit attracts organisa- 
ble matter from the stem through the stalk, and the 
seed from the fruit through its placenta* ; and this 
accounts, independently of other causes, for the 
importance of the fruit to the seed. 

102. When the seed is ripe it is dry, all its free 
water being parted with ; and its interior is occupied 
by starch or fixed oil, or some other such substance, 
together with earthy matters. It would seem that, 
so long as these secretions remain undecomposed, so 
long does the vitality of the seed continue unim- 
paired ; and hence the great age at which certain 
kinds of seeds have been found to grow. But, as it 
is difficult to prevent their decomposition, so is it 
difficult to preserve seminal vitality for any consider- 
able time ; and the difference found in the duration 
of the growing powers of seeds probably depends 
principally upon chemical differences in their consti- 
tuent parts. Oily seeds, which readily decompose, 



* The placenta is a soft part of the interior of a fruit, upon which 
the seed is formed. It is composed of thin-sided parenchyma, the 
most absorbent of all the forms of tissue, and is in communication, 
by its whole surface, with the parenchyma of the fruit. 

f Not to speak of the doubtful instances of seeds taken from the 
Pyramids haying germinated, Melons haye been known to grow at 
the age of 40 years, Kidney beans at 100, Sensitiye-PIant at 60, 
Rye at 40 ; and there are now growing, in the garden of the Horti- 
cultural Society, Raspberry plants raised from seeds 1600 or 1700 
years old. (See Introduction to Botany, ed. 3, p. 368.) 



78 VITAL ACTIOXS. 

are among the most perishable ; starchy seeds, which 
are least subject to change, are the most tenacious of 
life. 

103. Warmth, moisture, and an excess of oxygen, 
but especially warmth and moisture, while they are 
the greatest causes of germination, are probably, on 
that same account, the chief causes of death. Seeds 
remain dormant so long as the proportion of carbon 
peculiar to them is undiminished; water is decom- 
posed by their vital force (14) ; and its oxygen, com- 
bining with the carbon, forms carbonic acid, which 
is given off. The effect of access of water is, there- 
fore, to rob seeds of their carbon; and the effect 
of destroying their carbon is to deprive them of the 
principal means which they possess of preserving 
their vitality. 

104. Although a seed, if fully formed, is in all 
cases capable of perpetuating its race, yet there is 
a difference in the degree to which this capability • 
extends. All seeds will not equally produce vigor- 
ous seedlings : but the healthiness of the new plant 
will correspond with that of the seed from which it 
sprang. For this reason, it is not sufficient to sow a 
seed to obtain a given plant : but, in all cases where 
any importance is attached to the result, the plumpest 
and heaviest seeds should be selected, if the greatest 
vigour is required in the seedling ; and feeble or less 
perfectly formed seeds, when it is desirable to check 
natural luxuriance. It is apparently for this reason, 
that old Melon seed is preferred to new ; for the 
latter would give birth to plants too luxuriant for 



OF TEMPERATURE. 79 

fche small space in which the Melon can be cultivated, 
under the artificial circumstances required in this 
country. 

105. As both fruit and seeds are maintained at the 
expense of the leaves, the destruction of the former, 
when young, will enable the latter to store up against 
a succeeding season, for the support of future flowers, 
all that organisable matter which the fruits and seeds 
destroyed would have otherwise consumed.* 



CHAPTER VII. 

OF TEMPERATURE. 

Limits of Temperature endurable by Plants. — Effects of 
a too high Temperature — of a too hw Temperature. 
— Frost — Alternations of Temperature. — Day and 
Night. — Winter and Summer. — Temperature of 
the Eo,rth and Atmosphere* 

106. The extreme limits of temperature which 

* When any young trees or plants show forth fruit they are 
usually looked upon with great satisfaction, and allowed to mature 
as large a number as possible, by those who know little of such 
matters. It is almost invariably the ease, however, that such an 
over-crop on a young tree confirms that delicacy of constitution of 
which it is the index, and gives it for ever after a sickly and dwarf- 
ish habit. In all such instances the fruit should bo plucked off 
annually, till tiae tree or plant has attained vigor and size enough to 
enable it to mature its fruit without exhaustion. A. J. D. 



80 VITAL ACTIONS. 

vegetables are capable of bearing, without destruction 
of their vitality, have not been determined with pre- 
cision ; it is however known, that, on the one hand, 
certain seeds may be boiled without being killed, 
and that, on the other, they are capable of bearing 
many degrees of freezing without suffering. In like 
manner, some plants are found to endure the most 
intense cold known upon the globe, while others 
sustain, occasionally, a temperature as high as 140°, 
as was observed by Dr. Coulter on the banks of the 
Bio Colorado.* The number of plants, however, 
capable of sustaining extremes of temperature, is 
small, and the greater part of the species known to us 
are proved to exist within the limits of 32° and 90°. 
What amount of temperature a given species will 
prefer, under different circumstances, seems redu- 
cible to no general rule, but has to be deter- 
mined experimentally in each ease, or is judged of 
by the known climate of which a plant may be a 
native. It is probable that every species has a con- 
stitution better suited to some particular amount of 
temperature than to any other, although it can bear 
a greater or less degree without sustaining injury. 

107. Although many plants will live in a temper- 
ature much below that of freezing, yet no plant is 
able to grow unless the temperature is above 32°, for 
physical reasons that require no explanation. When 
temperature rises, the air contained in the minute 
cells of plants expands, the fluids become thinner, 

* The temperature borne by Oscillatorias in thermal springs is 
much higher than this ; but no such power is possessed by cultiva- 
ble plants. 



OF TEMPERATURE. 81 

the excitability of the tissue is aroused, and, at the 
same time, insensible perspiration is commenced, the 
effect of which is to bring into play the absorbing 
powers of the roots, and thus to set the machinery of 
vegetation in action. The degree of temperature 
required to produce this effect is extremely variable 
in different species of even the same climate, and is, 
of course, much more variable between plants of dif- 
ferent climates. For example, the common weeds 
called Chick-weed, Groundsel, and Poa annua, 
evidently grow readily at a temperature very near 
that of 82° ; while the Nettles, Mallows, and other 
weeds around them, remain torpid. In like manner, 
while our native trees are suited to bear the low tem- 
perature of an English summer, and, in most cases, 
suffer if they are removed into a country much 
warmer, such plants as the Mango, the Coffee, &c, 
inhabitants of tropical countries, soon perish, even in 
our warmest weather, if exposed to the open air. 

108. When, in the case of a given plant, the tem- 
perature is permanently maintained at a much higher 
degree than the species requires, it is over-excited. 
If the atmosphere is preserved in a proportional state 
of humidity, the tissue grows faster than the vital 
forces of the plants are capable of solidifying it, by 
the decomposition of carbonic acid, and by other 
means ; its excitability is gradually expended, the 
whole of its organisation becomes enfeebled, the vital 
functions are deranged, and a state of general debi- 
lity is brought on.* Such plants are soft and watery, 

* According to Mr. Knight, the effect of nn excessively high tern 

4* 



82 VITAL ACTIONS. 

with thin leaves, long joints, slender stems, and with 
no disposition to produce flowers. A slight lowering 
of temperature affects them more than a much greater 
lowering would have done under other circumstances ; 
and a permanent abstraction of light readily destroys 
them. Their inability to decompose carbonic acid, 
and to assimilate their food in proportion to their 
rate of growth, prevents their becoming so green as 
is natural to them, and gives them a pallid hue ; and, 
if it is their property to secrete other colouring mat- 
ter, that, like all their other secretions, is greatly 
diminished. But if, with a preternatural elevation 
of temperature, there is a proportionate abstraction of 
moisture, the loss of fluid, by perspiration and evapo- 
ration, goes on faster than the roots can make it 
good, or the tissue transmit it ; the secretions of the 
species are elaborated faster than the parts to receive 

perature is to cause, in unisexual plants, the production of male 
flowers only, while a very low temperature produces the contrary 
result. A Water Melon plant was grown in a house, the heat of 
which was sometimes raised to 110° during the middle of warm and 
bright days, and which generally varied, in such days, from 90° 
to 105°, declining during the evening to about 80°, and to 70° in the 
night ; the air was kept damp by copious sprinkling with water, of 
nearly the temperature of the external air, aud little ventilation 
was allowed. The plant, under these circumstances, grew with 
great health and luxuriance, and afforded a most abundant blossom ; 
but all its flowers were male. "This result," he says, "'did not, in 
any degree, surprise me ; for I had many years previously suc- 
ceeded, by long-continued very low temperature, in making Cucum- 
ber plants produce female flowers only ; and I entertain but little 
doubt that the same fruit-stalks might be made, in this and the pre- 
ceding species, to support either male or female flowers in obedience 
to external causes." {Hort. Trans, vol. iii. p. 460.) 



OF TEMPERATURE. 83 

them can be formed ; the old leaves " burn" and dry- 
up ; and young leaves perish, in like manner, as fast 
as they are formed. 

109. Such being the result of preternaturally higji 
temperature in dryness and in moisture, it is easy to 
conceive that, although such extremes cannot but be 
prejudicial, yet that they may be approached for parti- 
cular purposes with advantage. A high temperature 
and dryness will be favourable to the formation of se- 
cretions of whatever kind ; while a high temperature, 
with moisture, will lead to the production of leaves 
and branches only.* 

110. An unnaturally low temperature is productive 
of evils of another kind. A certain amount of heat 
is necessary to each particular species, to enable it to 
grow at all: the immediate effect of heat being to 
rouse the vital forces, and to bring them into action. 
If the amount of heat to which a plant is exposed be 
sufficient to effect this purpose, the functions of the 
plant are natural and healthy ; the consequences of 
exceeding it have been explained, those of diminish- 
ing it are not less disadvantageous. If the tempera- 
ture to which a growing plant is exposed is not low- 
ered so much as to destroy it, but just reduced to that 
point within which it will continue to live, the plant 
is brought, by the absence of a sufficient exciting 
cause, into a state not unlike that already described as 
resulting from over-excitement. It absorbs food from 

* According to Humboldt, this happens to the Wheat grown about 
Xalapa in Mexico, which will not mount into ear, but produces an 
abundance of grass, on which account it is cultivated as a fodder plant. 



84 VITAL A&HO&&, 

the earth and air, but it cannot assimilate it ; its tissue 
grows, but is not solidified by the incorporation of as- 
similated matter ; aqueous particles accumulate in the 
interior, a general yellowness ensues, partly from the 
want of a sufficient power of decomposing carbonic 
acid, and partly from inability to decompose the water 
collected in the interior."* The consequence of this is 
a want of the means of forming the usual secretions ; 
flavour, sweetness, nutritive matter, are each dimi- 
nished ; and the power of flowering and fruiting is 
lost, probably from the absence of a sufficient secre- 
tion of organisable matter (85). If the unhealthiness 
of the plant is not so great as to prevent the produc- 
tion of flowers, still they may not expand, as often 
happens to double roses in cold summersf in England ; 
or, if the flowers do unfold, the fertilising power of 

* The cause of the formation of different colours in different plants is 
too obscure a subject to suit the purpose of this work. It is, however, 
as well to observe that the effect of decomposing carbonic acid and ex- 
haling oxygen is the production of a green colour, the intensity of which 
is, in general, in proportion to the decomposing cause, that is to say, to 
light : but that, if from any circumstances water is not given off, but is 
retained in the system and allowed to accumulate, the green colour is 
altered and changes to yellow ; as if the vegetable blue, which must 
exist in combination with yellow in order to form green, were dis- 
charged. Such, indeed, is Macquart's explanation of the phenomenon ; 
and it appears most conformable to theory and fact For a short ex- 
planation of these and other opinions connected with vegetable colour- 
ing, see Introduction to Botany, ed. 3, book ii. chap. xvi. 

f Want of a sufficiently high temperature, and too much water in the 
soil, seem to be, either together or separately, the cause of the diffi- 
culty experienced by gardeners in making the Double yellow Rose ex- 
pand its flowers. 



OF TEMPERATURE. 85 

the pollen is impaired or destroyed, and no produc- 
tion of seed takes place. 

111. Should the temperature be so much lowered 
as to result in freezing, a destruction of some plants 
and injury to others take place, owing to physical 
causes quite different from those whose operation has 
been explained in the last paragraph. In what de- 
gree frost acts upon the vegetable fabric depends upon 
the specific nature of a plant ; the least frost destroy- 
ing some species, while others, under equal circum- 
stances, endure any known amount of natural cold : 
but, as general phenomena, it is in evidence, that, 
when a plant is frozen, the following effects are pro- 
duced : — 1st, The fluids contained within the cells of 
tissue are congealed, and consequently expanded; 
2nd, Such expansion produces, to some extent, a la- 
ceration of the sides of the cells, and impairs excita- 
bility by the unnatural extension to which the sides 
of the cells, if not lacerated, are subjected; 3rd, It 
expels air from the aeriferous cavities ; 4th, It also 
introduces air, either expelled from the air passages, 
or disengaged by the glacial decomposition of water, 
into parts naturally intended to contain fluid ; 5th, 
The green colouring matter and other secretions are 
decomposed : 6th, The vital fluid, or latex, is de- 
stroyed, and the action of its vessels paralysed ; 7th, 
The interior of the tubes, in which fluid is conveyed, 
is obstructed by a thickening of their sides. These 
phenomena may be considered in part mechanical, in 
part chemical, and in part vital. The two latter are 
beyond control, and probably depend either upon the 



86 VITAL ACTIONS. 

quality of fluid and organic matter, which may resist 
the action of cold in different degrees, according to 
their various modifications, or else upon specific vi- 
tality. Salt and water freeze at different tempera- 
tures, according to the density of the mixtures, from 
4° to 27° ; oil of turpentine at 14° ; oil of bergamot 
at 23° ; vinegar at 28° ; milk at* 30° ; water at 32° ; 
olive oil at 36° ; oil of anise at 50° ; and it is not to 
be doubted that, in like manner, the fluid contents of 
plants, which we know are infinitely modified, will 
resist the action of cold in very different degrees.* It 
is recognised indeed as a general law. that the diffi- 
culty of freezing water is in proportion to its density. 
112. The effect of congealing the aqueous particles 
contained in plants is, in itself, sufficient to cause such 
a derangement of function as may end in death, and 
the other supposed causes may be left out of conside- 
ration. It will thus follow that, omitting differences 
arising out of the peculiar nature of different species, 
plants will suffer from frost in proportion to the abun- 
dance and fluidity of their secretions ; those whose 
tissue is driest, and whose secretions are most dense, 
being the most capable of resisting frost. Hence young 
shoots are destroyed by a degree of cold which does 
not affect old shoots of the same species ; and hence, 
also, the diminished capability of " unripe" shoots, or 
of plants growing in wet situations, or of trees when 

* See a paper on frost in the Iransactions of the Horticultural So- 
ciety, new series, vol. ii. p. 308. [A copious abstract of Dr. Lindley's 
highly interesting memoir upon this subject will be fuund in the Ame- 
rican Journal of Science and Arts, for March, 1840. G.] 



ON TEMPERATURE. 87 

they first begin to vegetate, of enduring extreme 
cold.* 

113. The effect of cold is, as has been seen, to di- 
minish excitability ; of heat, to stimulate it : but, if the 
latter stimulus were constantly equal, it may be con- 
ceived that the excitability would soon become im- 
paired or expended. Nature has, however, provided 
against this result, not only by the fluctuations of tem- 
perature that occur at different periods of the day, but 
more particularly by the periodical fall of temperature 
at night and its rise during the day ; an arrangement 
intimately connected with all the vital actions of vege- 
tation. In the day, when light is strongest, and its 
evaporating and decomposing powers most energetic, 
temperature rises and stimulates the vitality of plants, 

* M. De Candolle gives the following as the laws of temperature 
with respect to its influence upon vegetation : — 

1. All other things being equal, the power of each plant, and 
of each part of a plant, to resist extremes of temperature, is in the 
inverse ratio of the quantity of water they contain. 

2. The power of plants to resist extremes of temperature is direct- 
ly in proportion to the viscidity of their fluids. 

3. The power of plants to resist cold is in the inverse ratio of the 
rapidity with which their fluids circulate. 

4. The liability to freeze, of the fluids contained in plants, is 
greater in proportion to the size of the cells. 

5. The power of plants to resist extremes of temperature is in 
a direct proportion to the quantity of confined air which the 
structure of their organs gives them the means of retaining in the more 
delicate parts. 

6. The power of plauts to resist extremes of temperature is in 
direct proportion to the capability which the roots possess of ab- 
sorbing sap less exposed to the external influence of the atmosphere 
and the sun. 



03 VITAL ACTIONS. 

so as to meet the demand thus made upon them ; then, 
as light diminishes, and with it the necessity for exces- 
sive stimulus, temperature falls, and reaches its mini- 
mum at night, the time when there is the least demand 
upon the vital forces of vegetation ; so that plants, like 
animals, have their diurnal seasons of action and re- 
pose. During the day, the system of a plant is ex- 
hausted of fluid by the aqueous exhalations that take 
place under the influence of sun-light ; at night, when 
little or no perspiration occurs, the waste of the day is 
made good by the attraction of the roots, and by morn- 
ing the system is again filled with liquid matter, ready 
to meet the demand to be made upon it on the ensuing 
day.* jSTo plants will remain in a healthy state unless 
these conditions be observed. 

11-4. The alternation of seasons seems to be intended 
to produce the like effects in a more extended manner; 

* The treatment of green-house plants by the majority of garden- 
ers, is directly opposed to the natural laws here so correctly stated. 
The gardener raises the temperature in a cold winter night very 
frequently much higher than it is in the day, and the dry heat 
stimulates the plants into an unnatural and sickly growth, when 
they ought to be resting. The heating apparatus of a good green- 
house should be so arranged as to afford a steady but rather low 
temperature at night, increasing towards morning, so that with the 
returning sunlight some ventilation can be allowed. In other words 
the plant-house should be at its lowest safe temperature about mid- 
night, and its highest at noon-day. But a3 usually managed, it is 
warmest and dryest at midnight, so that the system of the plant is 
doubly exhausted by the process of growth that takes place at that 
time. A. J. D. 

\ The incessant vegetation of arctic countries during their sum- 
mer is an exception to this rule ; but not such as to affect the general 
truth of the foregoing propositions. 



ON TEMPEKATUKE, 89 

so that the summer season may be regarded as one 
long day, and the winter as a night of similar duration. 
The long days, bright light, and elevated temperature 
of summer push the powers of vegetation to their 
limits ; towards the end of the season excitability be- 
comes impaired, all the vessels and perishable parts are 
worn out, leaves choke up and can neither breathe nor 
digest, and the system of a plant, by the incessant ex- 
halation of aqueous matter, becomes dried up, as it 
were, and exh austed . At that time, temperature keeps 
falling, and light diminishing, till at last, upon the 
arrival of winter, neither the one nor the other is suffi- 
cient to excite the vital actions, and a plant sinks into 
comparative repose. At this time, however, its vital 
actions are not arrested ; if they were, it would be dead 
or absolutely torpid ; they are only diminished in in- 
tensity. The roots continue to absorb from the soil 
food, which is slowly impelled into the system, whence 
it finds no exit; it therefore gradually accumulates, 
and in the course of time refills all those parts which 
the previous summer's expenditure had emptied. In 
the meanwhile the excitability of the plant is recovered 
by rest, and may be even conceived to accumulate with 
the food that the absorbent system of the roots is storing 
up. At length, when the temperature of the season 
has reached the requisite amount, excitability is once 
more aroused, an abundance of liquid food is ready to 
maintain it, and growth recommences ; rapidly or 
slowly in proportion to the amount of excitement, to 
the length of previous repose, and to the quantity of 
food which had been accumulated. In hot climates, 



90 VITAL ACTIONS. 

where winter is unknown, the requisite periodicity of 
stimulus and rest is provided for by what are called 
the dry and the rainy seasons ; the former being equi- 
valent to the winter, the latter to the summer, of north- 
ern latitudes. 

115. As plants have little power of generating heat, 
like animals, except in particular cases, and very lo- 
cally,* they are principally dependent upon the media 
that surround them for the heat which they require. 
Considering the great importance of heat in their 
economy, it is, for the purposes of gardening, a most 
necessary object to ascertain what proportion is usually 
borne to each other, in different countries, by the tem- 
peratures of the earth and atmosphere, the chief media 
by which plants can be affected. Upon the tempera- 
ture of the atmosphere there are numerous observa- 
tions in many countries ; upon that of the earth, so few 
as to afford no sufficient data for the solution of this 
problem. It is usually considered that the tempera- 
ture of springs affords sufficient evidence of the tempe- 
rature of the earth ; but, so far as vegetation is con- 
cerned, this evidence is unsatisfactory. Springs, de- 
riving their origin from considerable depths, have a 
nearly uniform temperature all the year round: but 
the temperature of the earth's surface varies with the 
seasons ; is extremely different in summer and winter ; 
and is affected by the quality of the soil, in proportion 
as that is more or less absorbent and retentive of heat. 

* Allusion is here, of course, made to the extrication of heat dur- 
ing the periods of flowering and germination, phenomena which 
have no obvious connexion with cultivation. 



OF TEMPERATURE. 



91 



"What we want to know, as respects vegetation, is, not 
the mean temperature of the earth at some distance 
from its surface, but the temperature immediately be- 
low the surface ; i. e. of that part of the soil into which 
the roots of plants penetrate, and whence they derive 
their food. It is also requisite that this should be as- 
certained monthly, so as to furnish the means of com- 
paring the terrestrial temperature with the periodical 
state of vegetation.* Such being the case the tempe- 



* The following proportions between the mean temperature of 
the earth, as indicated by springs, and that of the atmosphere, 
have been collected from various sources : — 



Berlin .... 
Carlstrom . . 
Upsal .... 
Paris .... 
Charleston . . 
Philadelphia 
Virginia . . . 
Massachusetts . 
Vermont . . . 
Raith .... 
Gosport . . . 
Kendal . . . 
Keswick . . . 
Leith .... 
South of England 
Torrid Zone . . 



Authority. 



Wahlenberg 

ditto 

ditto 
(Catacombs) 
Volney 

ditto 

ditto 
Dewey 
Volney 
Ferguson 
Watson 

ditto 

ditto 

ditto 
Rees' Cyclo. 
Volney 



Temp, of 
Earth. 



49-28 c 

47-30 

43-70 

53-00 

63-00 

53-00 

57-00 

47-21 

44-00 

47-70 

52-46 

47-20 

46-60 

47-30 

48-00 

63-00 



Mean 
Temp, of 
Atmo- 
sphere. 



46-40° 

42-03 

42-05 

51-00 

68-00 

53-42 

57-00 

44-73 

56-00 

47-00 

51-42 

47-04 

48-00 

48-36 

50-62 

81-50 



It must be obvious, from these returns, imperfect as they are, 
that the results are of little value with respect to vegetation, and 
that indications from springs, from their very nature, can be but 
little employed in inquiries where it is necessary to determine 
the fluctuating terrestrial temperature of the surface of the earth 
in different months. For example, Mr. Ferguson found the 



92 



VITAL ACTIONS. 



rature indicated by springs will be too high in winter 
and too low in summer; a most material error. 

116. From the observations of Mr. Ferguson, of 
Kaith, with thermometers buried at different depths 
in the ground, it appears, that in the years 1816 and 
1817, at that place, in 56° 10' N. lat, and 50 feet 
above the sea, the mean temperatures, indicated by 
geothermometers buried respectively to the depths of 
one foot and two feet, varied from 19° to 21° Fahr. 
between summer and winter, the earth being colder 
in winter and hotter in summer to that amount : and 
the highest mean observed was 55-2°, in July, 1817, 
at a foot below the surface.* Other observations, of 



temperature of a spring at Raith, 48 *l °; but the mean tempe- 
rature of the earth, one foot below the surface, was 43 "58°, and 
two feet, 44 , 55°. 

* Observations made on the Temperature of the Earth, at one and 
two feet below the Surface, in the Garden of Robert Ferguson, Esq., of 
Raith :— 



January . . , 

February . . , 

March . . . . 

April . . . . 

May . . . . 

June . . . , 

July . . . , 

August . . . 

September . . 

October . . , 

November . 

December . 

! Mean of Year 



1816. 


1817. 


One 


Two 


One 


Two 


Foot. 


Feet. 


Foot. 


Feet. 


33-0° 


36-3° 


35.6° 


38-7 


33-7 


36-0 


37-0 


40-0 


35-0 


3G-7 


39-4 


40 2 


39-7 


38-4 


45-0 


42-4 


40-0 


43-3 


46-8 


44-7 


51'6 


50 


511 


49-4 


54-0 


52-5 


55-2 


55-0 


50-0 


5 2 "5 


53-4 


53-9 


51-6 


51-3 


53-0 


;»2-7 


47-0 


49-3 


45 7 


49-4 


40-8 


43-8 


41-0 


44-7 


35*7 


40-0 


35-9 


40-8 


43-8 


44 T 


44 9 


45-9 



OF TEMPERATURE. 93 

a similar kind, have been made in the garden of the 
Horticultural Society, from which we learn that, in 
the valley of the Thames, the maximum mean of ter- 
restrial temperature, at one foot below the surface, 
has been found to be 64'81° in July, which is the 
hottest month of the year ; but that the greatest differ- 
ence between the mean temperature of the earth and 
atmosphere is in the month of October, when it 
amounted, in the two years during which the ob- 
servations were made, to between 3 and 4 degrees ; 
and that, in general, the mean temperature of the 
earth, a foot below the surface, is at least one degree, 
and more commonly a degree and a half, above the 
mean of the atmosphere. In these cases, if the ter- 
restrial temperatures be compared with those of the 
atmosphere, it will be found that in the spring, when 
vegetation is first generally set in motion, the tempe- 
rature of the earth not only rises monthly, but re- 
tains a mean temperature higher than that of the 
atmosphere by from one to two degrees ; and that, in 
the autumn, when woody and perennial plants re- 
quire that their tissue should be solidified, and their 
secretions condensed, in order to meet the approach 
of inclement weather, the terrestrial temperature re- 
mains higher in proportion than that of the atmo- 
sphere, the earth parting with its heat very slowly.* 
117. There appears to be no series of direct ob- 
servations, upon the superficial temperature of the 
earth, at the different periods of vegetation, in other 

* Quarterly Averages of Temperature obtained from Thermometers 
buried in the Earth in the Garden of the Horticultural Society ; re- 



94 



VITAL ACTIONS. 



countries; but some statements are to he found, here 
and there, concerning the temperature occasionally 
observed, from which it is to be inferred, that the 
earth is heated, at least for short periods of time, very 
much above the atmosphere ;* and it is probable that 
this excessive elevation of temperature is necessary to 

duced from the Register kept by Mr. Robert Thompson, by order of 
the Garden Committee : — 







Earth. 


Mean of 
Atmo- 
sphere. 




One i Two 
Foot. 1 Feet. 


1837. July, August, September, . . 
October, November, December, 

1838. January, February, March, . . 

April, May, June, 

July, August, September, . . 
October, November, December, 

1839. January, February, March, . . 




62-19° 61 
46-13 I 47 

37-21 ! 38 
5 2 "2 3 50 
62-15 j 61 
45-83 |47 
10-21 41 
53*05 ! 51 


4'J C 

85 

71 

09 

30 

53 

37 


60-44° 

43-86 

34.57 

52-01 

60-23 

43-28 

39-51 

52-18 




m, 




Average monthly mean, from July, 18 
to June, 1839, inclusive, 


49-87 ! 50-15 


48-26 



* Memoranda concerning the Temperature immediately below the 
Surface of the Earth, occasionally remarked in different Countries : — 

Egypt 



Tropics 
Oronoco 



France 



133° — 144°. 1 According to Edwards 

and Colin. 

Often 126°— 134°. iHumboldt, Fragm. As. 

Coarse white sand at Humboldt. 
140°, the atmosphere 



Chile 

New Grenada 

Cape of G. Hope 

Bermuda 



being 84-5°, 
118°— 122°; once 127' 

the atmosphere being 

91-5°. 
113°— 118° among dry 

grass. 
85° usual summer temp. 

1 foot below surface. 
159° under the soil of a 

bulb garden. 
142° thermometer bare- 
ly covered. 



Arago as quoted by Ed- 
wards and Colin. 

Boussingault. 

Hay, in London's Gard. 

Mag. vi. 437. 
Herschel [MSS.\ 

Col. Emmett 



OF TEMPERATURE. 95 

the healthy condition of many plants. From some 
interesting observations communicated to me by Sir 
John HerscheJ, it appears that the temperature of the 
earth, at the Cape of Good Hope, is often excessive. 
On the 5th of December, 1837, between one and two 
o'clock in the day, he observed the heat, under the 
soil of his bulb garden, to be 159° ; at 8 P. M. it was 
150°, and even in shaded places 119° : the tempera- 
ture of the air in the shade, in the same garden, at the 
same period, was 98° and 92°. At 5 P. M. the soil of 
the garden having been long shaded, was found to 
have, at 4 inches in depth, a temperature of 102°. 
" On the 3d of December, a thermometer buried i inch 
deep, in contact with a seedling fir of the year's plant- 
ing, quite healthy, and having its seed-leaves, marked 
as follows:— at Ilk 25 m. a. m. 148-2°, at Oh. 48m. 
P. M. 149-5°, at Ik 34m. p. m. 149-8°, at lh. 54m. P. 
M. 150-8°, and at 2k 46m. p. m. 148°." Sir John 
Herschel observes that such observations "go to show 
that at the Cape of Good Hope, in the hot months, 
the roots of bulbous and other plants which do not 
seek their nourishment very deep, must frequently, 
and, indeed, habitually, attain temperatures which 
we can only imitate in our hothouses by actually sus- 
pending over the soil plates of red-hot iron. For it 
must be remarked, that heating the ground from be- 



Lantao, China 



Water of rice fields 113°: 
adjacent sandy soil 
much higher; for to- 
wards midday the 
black sides of the boat 
were 142°5Q. 



Meyen. 



96 VITAL ACTIONS. 

low would not distribute the temperature in the same 
way." 

These observations seem to confirm the late Mr. 
Harvey's suspicions, that the real force of the sun's 
rays in tropical countries is still far from being ascer- 
tained. When, therefore, we are informed by tra- 
vellers that the temperature in the sun, at Gondar, 
has been seen to be 113° (Bruce); at Benares, 110°, 
113°, 118° (Harvey) ; or at Sierra Leone, 138° (Win- 
terbottom) ; it must be supposed that, in reality, the 
temperature would have been found much higher in 
those places, had more efficient means of observation 
been employed. Mr. Foggo, indeed, succeeded, by 
means of a large thermometer, having the ball covered 
with black wool, and fully exposed to the direct rays 
of the sun, unsheltered from the wind, in obtaining, 
at Edinburgh, on the 29th of July, at 3h. 10 P. m., an 
indication of 150°, and at 2b. P. M. of 140° ; while 
another instrument, similarly prepared, and resting 
in contact with herbage, was found to indicate onl} r 
119° and 110°; so that, as Mr. Foggo remarks, a differ- 
ence of 30° was produced in these cases solely from 
the manner in which the instruments were exposed. 
(Edinburgh Philosophical tJowrnal, No. xxvii.) 

118. For horticultural purposes, a very extensive 
series of observations requires to be made at a very 
great number of different places, with a view to deter- 
mine the connexion between the temperature of the 
soil and the seasons of vegetation ; for it does not 
appear that any such have yet been recorded, except 
in this country, where, from their fewness, they are 



OF TEMPERATURE. 97 

by no means so satisfactory as could be desired. In 
making these, the nature of the soil in which the 
thermometers are plunged, should, among other 
circumstances, be very precisely described ; for it 
is obvious that the result will be essentially affected 
by the peculiar conducting power of the earth. 

119. But although we have no geothermometrical 
observations which have a direct relation to the con- 
nexion between terrestrial temperature and vege- 
tation, yet an approximation to the amount of heat in 
the earth may perhaps be obtained indirectly. It 
seems improbable that the surface of the earth should 
be colder than the mean temperature of the air that 
rests upon it ; and it seems certain, from the evidence 
afforded by this country (116), that, in fact, it is 
at least a degree or two above it ; therefore, in the 
tropical parts of America, where Humboldt found 
the mean temperature of the coldest month not to be 
lower than 79*16° at Cumana, we shall be justified in 
concluding that the temperature of the earth's surface 
never falls permanently below that amount ; and as 
the mean summer temperature* of the place was 
found to be 82*04°, so it is probable that the earth 
will have something above that degree of warmth, on 
an average, in the summer. f 

* For the warmest month, this great observer gives 84 - 38° as 
the mean ; which corresponds remarkably with the temperature 
a foot below the surface in New Grenada, where, according to 
a correspondent of Mr. Hay, it is 85° during summer, "as a gen- 
tleman, a planter there, wrote home for his information." (See 
London's Gard. Mag., vi. 437.) 

f [The mean temperature of the State of New- York, for fourteen 

5 



98 VITAL ACTIONS. 

*#* To collect together evidence as to the real 
amount of temperature at the different seasons of 
vegetation, in various parts of the globe, -would be to 
render a most important service to horticulture ; for 
it is hopeless to expect that the cultivation of plants 
can be perfect, in the absence of one of the first data 
that require to be ascertained. What, for instance, 
are the terrestrial and atmospheric temperatures of 
the melon fields of Persia, Bokhara, Spain, or Smyrna, 
where that delicious fruit acquires its greatest ex- 
cellence ? In the meanwhile, the few facts recorded 
in the following table will serve to show the prac- 
tical importance of such information, it being borne 
in mind that, as has been already shown (119,) the 
mean temperature of the soil will probably be, on an 
average, a degree or two above the recorded means 
of the warmest and coldest months. Thus, the tem- 
perature of the earth at Calcutta, for instance, may 
be computed to be not more than 88°, nor less than 
72° ; and if we compare places so similar in climate 
as Marseilles, Vienna, and London, it will be found 

years, (from 1826 to 1839 inclusive,) as deduced from observations 
made under the direction of the Regents of the University, and 
embodied in their Report for 1840, is 44-31° Fahr. The lowest mean 
for a single year of observations at many stations, is 44 11° (1836); 
the highest, 49'99° for (1828.) The mean temperature of the 
■warmest and coldest months, for a series of years, have not been 
embodied, but somewhat ample data have been collected. At 
Albany, the mean temperature of the coldest month for 1889 
(January) was 23-38°; of the warmest month (July), 72-88°. On 
Long Island, near the city of New-York, the mean temperature of 
the coldest month in the same year was 28 -89, and of the warmest 
(July) 70-69°. G.] 



OF TEMPERATURE. 99 

that the difference in the terrestrial temperature, 
as indicated by that of the atmosphere in the warmest 
month of summer, is quite sufficient to explain why 
we have so little success in the cultivation of the vine 
in the open air in England. 



100 



VITAL ACTIONS. 



120. A Table of Mean Temperatures of the 
hottest and coldest months : 









Mean Temp, of 






Latitude. 


Longitude. 






Authorities. 




Warm- 


Coldest 


St. Petersburg 






est 
Month- 


Month. 




59°56' X. 


30°19' E. 


65-66° 


8-60° 


Humboldt. 


Moscow 


55 45 X. 


37 32 E. 


70-52 


6-08 


ditto. 


Melville Is- j 
land . . } 


74 47 N. 


110 48 W. 


39-08 


—35-52 


Hugh Murray 






42-41 


—32-19 


Ed. Phil. Journal. 


Copenhagen 
Edinburgh . 


55 41 X. 


12 35 E. 


65-66 


27-14 


Humboldt. 


55 57 X. 


3 10 W. 


59-36 


38-30 


ditto. 


Geneva . 


46 12 X. 


6 8 E. 


66*56 


34-16 


ditto. 


Vienna . . 


48 12 MT. 


16 22 E. 


70-52 


26-60 


ditto. 


Paris . . . 


48 50 N". 


2 20 E. 


65-30 


36-14 


ditto. 


London . . 


51 30 N. 


5 W. 


64-40 


37-76 


ditto. 


Philadelphia 


39 56 N. 


75 16 W. 


77-00 


32*72 


ditto. 


Xew-York . 


40 40 N. 


73 58 W. 


80-70 


25-34 


ditto. 


Pekin . . . 


39 54 IS. 


116 27 E. 


84-38 


24-62 


ditto. 


Milan . . . 


45 28 N. 


9 11 E. 


74-66 


36-14 


ditto. 


Bordeaux . 


44 50 N. 


34 W. 


73-04 


41-00 


ditto. 


Marseilles . 


43 17 X. 


5 22 E. 


74-66 


4442 


ditto. 


Rome . . . 


41 53 N. 


12 27 E. 


77-00 


42-26 


ditto. 


Funchal . . 


32 37 X. 


16 56 W. 


75-56 


64-04 


ditto. 


Algiers . . 


36 48 X. 


3 1 E. 


82.76 


60-08 


ditto. 


Cairo . . . 


30 2 X. 


30 18 E. 


85-82 


56-12 


ditto. 


Vera Cruz . 


19 11 X. 


96 1 W. 


81-86 


71-06 


ditto. 


Havana . . 


23 10 X. 


82 13 W. 


83-84 


69.98 


ditto. 


Cumana . . 


10 27 X. 


65 15 W. 


84.38 


79-16 


ditto, [endar. 


Canton . . 


23 10 N. 


113 13 E. 


84-50 


57-00 


Anglo-Chin. Cal- 


Macao . . 


22 10 X. 


113 32 E. 


86-60 


63-50? 


ditto. 


Canaries . . 


28 30 X. 


16 00 W. 


78-90? 


63-70 


Brande's Journal. 


Lohooghat, ) 










C Transac. Med. 


(5S00 feet [ 


29 23 X. 


79 56 E. 


69-34 


43-57 


-j Phy's Soc'y. 
( Calc. 


above the sea) \ 










Fattehpiir . 


25 56 X. 


80 45 E. 


74-94 


58-74 


Gleanings in Sci. 


Gurra-wurrah 


23 10 N. 


79 54 E. 


87-45 


60-23 


ditto. 


Calcutta . •] 


22 40 X. 


88 25 E. 


85-70 


66-20 


ditto. 




. . . 


86-86 


70-10 


Journ. As. Soe. 


Ava . . 


21 51 X. 


95 98 E 


88-15 


64-12 


Gleanings in Sci. 


Bareilly . . 


28 23 X. 


79 23 E. 


91-91 


56-50 


ditto/ 


Chunar . . 


25 9 X. 


82 54 E. 


90-00 


58-00 


Ed. Ph. Journ. 


Cape of G'd ) 












Hope [ 


34 23 S. 


18 25 E. 


74-27 


6743 


Herschel, MSS. 


(Feldhausen) \ 










[MSS. 


Bahamas 


26 30 X. 


78 80 W. 


33-52 


69-07 


tlon. J. C. Lees, 


Swan River . 


32 00 S. 


115 50 E. 78-00 


54-84 


Milligan. 
Col. Emmett. 


Bermuda . 


32 15 X. 


64 80 7V. 176-75 


57-90 



BOOK II. 

OF THE PHYSIOLOGICAL PRINCIPLES UPON WHICH 
THE OPERATIONS OF HORTICULTURE ESSENTIALLY 
DEPEND. 

Every operation in horticulture depends for suc- 
cess upon a correct appreciation of the nature of the 
vital actions described in the last Book ; for although 
there have been many good gardeners entirely unac- 
quainted with the science of vegetable physiology, and 
although many points of practice have been arrived at 
altogether accidentally yet it must be obvious that the 
power of regulating and modifying knowledge so ob- 
tained cannot possibly be possessed, unless the external 
influences by which plants are affected are clearly un- 
derstood. Indeed, the enormous difference that exists 
between the skill of the present race of gardeners and 
their predecessors can only be ascribed to the general 
diffusion, that has taken place, of an acquaintance with 
some of the simpler facts in vegetable physiology. 

In attempting to apply the explanations of science 
to the routine of horticultural practice, it appears de- 
sirable, in order to avoid frequent repetition, that all 
the subordinate details of the art should be omitted, 
and that those general operations should alone be ad- 
verted to which, under many different modifications, 
and in various forms, constitute the foundation of 
every gardener's education. 



102 APPLICATION OF PRINCIPLES. 

CHAPTEE I. 

OF BOTTOM HEAT. 

This term is, in common practice, made use of only 
in those cases where the temperature of the soil in 
which plants grow is artificially raised considerably 
above that which we are acquainted with in England ; 
and there seems to be a general idea that such an artifi- 
cial elevation of temperature is only necessary in a few 
special instances. It has, however, been shown (116), 
that the mean temperature of that part of the soil in 
which plants grow is universally somethinghigher than 
that of the air by which they are surrounded, and con- 
sequently it appears that nature, in all cases, employs 
some degree of bottom heat as a stimulus and protec- 
tion* to vegetation. At the same time, it must be ad- 

* That the warmth of the soil acts as a protection to plants 
may be easily understood. A plant is penetrated in all direc- 
tions by innumerable microscopic air passages and chambers, so 
that there is a free communication between its extremities. It 
may therefore be conceived that if, as necessarily happens, the 
air inside the plant is in motion, the effect of warming the air in 
the roots will be to raise the internal temperature of the whole in- 
dividual ; and the same is true of its fluids. Now, when the tem- 
perature of the soil is raised to 150° at noonday by the force of the 
solar rays, it will retain a considerable part of that warmth 
during the night : but the temperature of the air may fall to such 
a degree that the excitability of a plant would be too much and 
suddenly impaired, if it acquired the coldness of the medium 
surrounding it ; this is prevented, we may suppose, by the 



OF BOTTOM HEAT. 103 

mitted that, in some cases, the amount is extremely 
small ; for Yon Baer found Ranunculus nivalis and 
Oxyria reniformis flowering in Nova Zembla, where 
the soil was not warmed above 341°; and, in Jakutzsk, 
Erdmann states that Summer Wheat, Rye, Cabbages, 
Turnips, Radishes, and Potatoes are cultivated, al- 
though the ground is not thawed above three feet in 
depth. 

That elevating the temperature of moist soil causes 
an unusual degree of vigour in plants unaccustomed 
in nature to such an elevation, is a fact which requires 
no proof: it is attested by the condition of vegetation 
round hot springs, and in places artificially heated by 
subterraneous fires ; and this has probably been the 
cause of the employment of tan and hotbeds, by which 
means bottom heat has been generally obtained for 
rearing delicate species, and especially seeds. But if 
this stimulus acts in the first instance beneficially in all 
cases alike, it soon becomes a source of mischief in 
those species which are natives of climates where such 
terrestrial heat is unknown, the latter "drawing up," as 
the saying is, becoming weak and siekl}', and speedily 
presenting a diseased appearance (108). 

On the other hand, it is equally well known that, 
unless the temperature of the soil be raised permanent- 
ly to at least 75°, the seeds of tropical trees will not 
germinate ; or, if they do, they push forth feebly, and 

•warmth communicated to the general system from &*e soil, 
through the roots ; so that the lowering of the temperature of the 
air, by radiation during the night, is unable to affect plants injuri- 
ously in consequence of the antagonist force exercised by the 
heated soiL 



104 APPLICATION OF PRINCIPLES. 

from the first present the sickly appearance of plants 
suffering from cold (110). Hence arises the impossi- 
bility of making the seeds of tropical plants germinate- 
when sown in the open air in this country 7 where the 
mean temperature of the earth seldom rises to 65°, 
and that for only short periods of time. It is, there- 
fore, obvious that all plants require some bottom heat \ 
but the amount varies with their species, and the only 
means or power of determiniDg what the amount 
should be, is afforded by the known degree of warmth 
of the climate of which a plant may be a native. 

When plants are cultivated in glass houses, there is 
little difficulty in supplying them with the amount of 
bottom heat which they may require ; but this can 
either not be effected at all, or only to a limited degree, 
by a selection of soils and situations, when plants are 
cultivated in the open air ; and hence one of the many 
difficulties of acclimatising in a cold country the spe- 
cies of a warmer climate. It is true that plants will 
exist within wide limits of temperature, and, conse- 
quently, a few degrees of difference in the natural bot- 
tom heat to which they are exposed may not affect 
them so far as to destroy them; but it cannot be 
doubted that the conditions most favourable to their 
growth are those which embrace a temperature rather 
above than below that to which they are accustomed 
in their native haunts. 

The Orange tree is found in perfection where the 
temperature of the soil maybe computed to rise to 80° 
or 85°, and never to fall below 58°, as in the Bermu- 
das, Malta, and Canton. How injudicious, then, is 



OF BOTTOM HEAT. 105 

our practice of exposing it during summer to the open 
air, in tubs, where the soil scarcely rises in tempera- 
ture above 66°, and preserving it during winter in 
cold conservatories, the soil of which often sinks to 
36° ; under such circumstances the Orange exists in- 
deed, but where are the perfume and juiciness of its 
fruit, and where the healthy vigour of its noble foliage? 
The Vine cannot be grown in the open air of this 
country to any useful purpose, except when trained 
to walls, in soils and situations unusually exposed to 
the beams of the sun ; it is only then that it can ob- 
tain for its roots such a permanent warmth of 75°, 
which it will have at Bordeaux, or 80° in Madeira. 

It may hence be considered an axiom in horticul- 
ture, that all plants require the soil, as well as the at- 
mosphere, in which they grow, to correspond in 
temperature with that of the countries of which they 
are natives. It has also been alreadj 7 shown, that the 
mean temperature of the soil should be a degree or two 
above that of the atmosphere (119). 

This explains why it is that hardy trees, over whose 
roots earth has been heaped or paving laid, are found 
to suffer so much, or even to die ; in such cases, the 
earth in which the roots are growing is constantly 
much colder than the atmosphere, instead of warmer. 
We have here,* also, the cause of the common circum- 

* Mr. Knight long since mentioned an important fact con- 
nected with this subject: — "It is well known," he said, "that 
the bark of Oak trees is usually stripped off in the spring, and 
that in the same season the bark of other trees may be easily 
detached from their alburnum, or sap-wood, from which it is, at 

5* 



106 APPLICATION OF PRINCIPLES. 

stance of Vines that are forced early not setting theii 
fruit well, when their roots are in the external border 
and unprotected by artificial means ; and to the same 
cause is often to be ascribed the shrivelling of grapes, 
which, as we all know, most commonly happens to 
Vines whose roots are in a cold and unsunned bor- 
der. 

Mr. Reid of Balcarras has, indeed, shown that one 
of the causes of canker and immature fruit even in 
orchards is the coldness of the soil. He found that, in 
a cankered orchard, the roots of the trees had entered 
the earth to the depth of 3 feet; and he also ascertained 
that, during the summer months, the average heat of 

that season, separated, by the intervention of a mixed cellular 
and mucilaginous substance ; this is apparently employed in the 
organisation of a new layer of fibre, or inner bark, the annual 
formation of which is essential to the growth of the tree. If, at 
this period, a severe frosty night, or very cold winds, occur, the 
bark of the trunk, or main stem, of the Oak tree becomes again 
firmly attached to its alburnum, from which it cannot be sepa- 
rated until the return of milder weather. Neither the health of 
the tree, nor its foliage, nor its blossoms, appear to sustain any 
material injury by this sudden suspension of its functions ; but 
the crop of acorns invariably fails. The Apple and Pear trees 
appear to be affected to the same extent by similar degrees of 
cold. Their blossoms, like those of the Oak, unfold perfectly 
well, and present the most healthy and vigorous character ; and 
their pollen sheds freely. Their fruit, also, appears to set well ; 
but the whole, or nearly the whole, falls off just at the period 
when its growth ought to commence. Some varieties of the 
Apple and Pear are much more capable of bearing unfavourable 
weather than others ; and even the Oak trees present, in this 
respect, some dissimilarity of constitution." (Hort. Trans., vi 
229.) 



OF BOTTOM HEAT 107 

the soil, at 6 inches below the surface, was 61° ; at 
9 inches, 57° •; at 18 inches. 50°; and at 3 feet, 44°. 
He took measures to confine the roots to the soil near 
the surface, and the consequence was, the disappear- 
ance of canker, and ripening of the fruit. {Memoirs 
of Caledonian HorL Soc* vi. part 2 ; and Gardener's 
Magazine, vii, 65.)* 

If, on the other hand, we take cases of growth in 
the artificial climate of hot-houses, we find that Bigno- 
nia venusta, and many other tropical plants, will not 

* This must be understood by our readers as applicable to the 
-climate -ci England, In that temperate and damp climate, the great 
drawback to the cultivation is the coldness of the soiL In this 
country, where there is five times more sunshine and heat than in 
Great Britain, the drawback is of the opposite kind, viz, the dry- 
ness and want of moisture in the soil during a good part of the sum- 
mer. Instead, therefore, of its being desirable to confine the roots 
near the surface, 'we find it of the greatest advantage in almost any 
species of culture, and especially for fruit-trees, to deepen the soil 
by trenching or sub-soil ploughing, so that the roots can run 
down twice the usual depth. This not only gives them a larger 
area from which to obtain their food, but, by placing the food 
deeper, it maintains that moisture and temperature which enable 
the roots to go on supplying the demands of the leaves, and keeping 
up growth, when trees in shallow soil cease growing, and 
become parched and starved by the heats of midsummer. We 
may add that canker, or a diseased state ■of the sap, usually arises in 
this country, not from coldness of the soil, but from sudden alterna- 
tions of temperature. The blights of the pear, apricot, and other 
trees, the most fatal diseases in the United States, are forms of 
canker induced by sudden thawing of the sap vessels after severe 
frost. Except in New England and the extreme northern portions 
of the country, a northern exposure Is found preferable to a southern 
one for orchards and fruit gardens, oa account of the greater uni- 
formity of temperature, and the much lessened tendency to disease 
in the trees s© situated A, J. D 



108 APPLICATION OF PRINCIPLES. 

flower unless in a high bottom heat ; and that Palm 
trees, planted in the soil of conservatories which it is 
impracticable to heat sufficiently, soon become un- 
healthy. 

The reason why it is necessary to plants in a grow- 
ing state, that the mean temperature of the earth 
should be higher than that of the air, is sufficiently 
obvious. Warmth acts as a stimulus to the vital 
forces (17), and its operation is in proportion to its 
amount, within certain limits. If, then, the branches 
and leaves of a plant are stimulated by warmth to a 
greater degree than the roots, they will consume the 
sap of the stem faster than the roots can renew it ; 
and, therefore, nature takes care to provide against 
this by giving to the roots a medium permanently 
more stimulating, that is, warmer, than to the branches 
and leaves. 

Such being the fact, it is obvious that one of the 
first of a gardener's cares should be, to secure the 
means of insuring a proper temperature to the soil in 
which he grows his plants, and that this is requisite 
for hardy as well as tender species ; and I entertain 
little doubt that the time is at hand when it will be 
considered quite as necessary to furnish heat for the 
soil as for the air ; not, however, heat without mois- 
ture, for that would evidently produce much greater 
evils than it was intended to cure, as has indeed been 
found by inconsiderate experimenters, I quite agree 
with Mr. Writgen in believing that it is the tempera- 
ture and moisture of a soil, much more than its mine- 
ralogical quality, that determine its influence upon 



OF BOTTOM HEAT. 109 

vegetation. (See Erster Jahresbericht, &c, am Mittel 
und Nieder-Rhein, p. 64.) 

Mr. Fintelmann, the king of Prussia's gardener at 
Potsdam, is celebrated for his success in the difficult 
art of forcing Cherries, and he has given an account 
of his practice, (Gard. Mag., vol. iii. p. 64,) in which 
it appears that the most peculiar feature is the strict 
attention he pays to the temperature of the roots. He 
first soaks the roots in water heated by the mixture of 
equal parts of boiling and cold water ; he afterwards 
sprinkles the trees with luke-warm water, and he con- 
tinues to employ it of the same temperature as long as 
watering is required. 

It seems, indeed, clear, that the success of the Dutch 
in obtaining an abundance of fresh vegetables, such as 
Lettuces, during the whole winter, is in part owing to 
their being able to maintain a gentle bottom heat. Ko 
doubt this is connected with the abundant light which 
their forcing structures admit, a,nd with other causes of 
considerable importance ; but none of those causes can 
be suppossed likely, in the absence of the bottom heat, 
to produce such a result as the Dutch gardeners 
obtain. 

If it is necessary that the temperature of the soil in 
which plants grow should be carefully regulated, and 
adjusted to their natural habits, it is no less requisite 
that the water in which aquatics are cultivated should 
be also brought to a fitting heat. Mr. William Kent 
succeeded well in making many tropical species flower, 
by growing them in lead cisterns plunged in a tan-bed, 
{Hort. Trans., iii. 34,) in a close heat. In like manner, 



110 APPLICATION OE PRINCIPLES. 

Mr. Christie Duff procured flowers in abundance from 
Nymphsea rubra, cosrulea, and odorata,by placing them 
in a cistern in a pine stove upon the end flues, where 
the fire enters and escapes ; or by plunging them into 
tan-beds in pine houses, varying in temperature from 
80° to 100°. {Hort. Trans., vii. 286.) Very lately, 
Mr. Sylvester, of Chorley, in Lancashire, obtained fine 
flowers from Nelumbium luteum, by paying attention 
to the temperature of water. When he kept the 
latter at 85°, the plants grew vigorously, and were in 
perfect health, but flowerless ; but by lowering it to 
70°-75°, which more nearly approaches the heat to 
which the plant is naturally accustomed, the magnifi- 
cent blossoms were produced and succeeded by seeds ; 
the red Nelumbium, however, which inhabits countries 
with a greater summer heat than the }*ellow, at the 
same time suffered by this lowering of temperature, 
none of its blossom buds having been able to unfold. 
(BoL Mag., xiii. n. s. t. 3753.) The water of rice 
fields, in which the red Nelumbium flourishes, was 
seen by Meyen at 113°, at Lantao, in China, (117). 

An opinion has, nevertheless, been entertained, that 
bottom heat is useless ; there is in the Horticultural 
Transactions (vol. iii. 288,) a paper to show that it is 
injurious ; and the authority of Mr. Knight has been 
referred to in support of the opinion, in consequence 
of that great horticulturist having expressed a belief 
that the u bark-bed is worse than useless." (Eort 
Trans., iv. 73.) But Mr. Knight repeatedly disavowed 
entertaining any such sentiments. In one place, he 
stated that the temperature of the air of the stoves in 



OF BOTTOM HEAT. Ill 

which his Pine-apple and other stove plants grew, 
without bark or other hot-bed, usually varied from 70° 
to 85° ; and that the mould in his pots, being sur- 
rounded by such air, acquired and retained, as it ne- 
cessarily must, very near the same aggregate tempera- 
ture, but subject to less extensive variation (Gard. 
Mag., v. 365) : in another, he says the temperature of 
the air was varied in his stove generally from about 
70° to 85° of Fahrenheit ; and he ascertained, by 
keeping a thermometer immersed in the mould of the 
pots, that the temperature of the soil varied yerj con- 
siderably less than that of the air of the stove ; the 
mould being in the morning generally some degrees 
warmer than the air of the house, and in the middle 
of the day, and early part of the evening, some de- 
grees cooler. {Hort. Trans., vii. 255.) 

It is, therefore, clear that he considered a high tem- 
perature necessary for the roots of his Pine-apple 
plants ; and we find, from one of his papers, {Hort. 
Trans., iv. 544,) that he considered it better to obtain 
the requisite temperature from the atmosphere than 
from a bark-bed, the usual source of bottom heat, " be- 
cause its temperature is constantly subject to excess 
and defect;" and he even admitted that if the bark- 
bed could be made to give a steady temperature of 
about 10° below that of the day temperature of the air 
in the stove, Pine plants would thrive better in a com- 
post of that temperature than in a colder. 

It is, therefore, plain that the dispute about bottom 
heat was not as to the necessity of it, but as to the man- 
ner of obtaining it, which, as it concerns the art of 
gardening, I need not further notice. 



112 APPLICATION OF PRINCIPLES. 

We have, doubtless, much to learn, as to the pro- 
per manner of applying bottom heat to plants, and as 
to the amount they will bear under particular circum- 
stances. It is, in particular probable that in hot- 
houses plants will not bear the same quantity of bot- 
tom heat as they receive in nature, because we can- 
not give them the same amount of light and atmos- 
pheric warmth ; and it is necessary that we should 
ascertain experimentally whether it is not a certain 
proportion between the heat of the air and earth that 
we must secure, rather than any absolute amount of 
bottom heat. 

It may also be, indeed it no doubt is, requisite 
to apply a very high degree of heat to some kinds 
of plants at particular seasons, although a very much 
lower amount is suitable afterwards ; a remark that 
is chiefly applicable to the natives of what are called 
extreme climates, that is to say, where a very high 
summer temperature is followed by a very low winter 
temperature. Such countries are Persia, and many 
parts of the United States, where the summers are 
excessively hot, and the winter's cold intense. The 
seeming impossibility of imitating such conditions 
artificially will probably account for many of the dif- 
ficulties we experience in bringing certain fruits, the 
Xewtown pippin, the cherry, the grape, the peach, 
and the almond, to the perfection they acquire in 
other countries. 

This subject will be frequently recurred to here- 
after. 



OF THE MOISTURE OF THE SOIL. 118 

CHAPTER II. 
OF THE MOISTURE OF THE SOIL.— W ATE RING. 

It has already (38) been shown that water is one 
of the most important elements in the food of 
plants, partly from their having the power of decom- 
posing it, and partly because it is the vehicle through 
Avhich the soluble matters found in the earth are con- 
veyed into the general system of vegetation. Its 
importance depends, however, essentially upon its 
quantity. 

We know, on the one hand, that plants will not 
live in soil which, without being chemically dry, con- 
tains so little moisture as to appear dry ; and, on the 
other hand, an excessive quantity of moisture, is 
in many cases, equally prejudicial. The great points 
to determine are, the amount which is most conge- 
nial to a given species under given circumstances, 
and the periods of growth when water should be 
applied or withheld. 

When a plant is at rest, that is to say, in the winter 
of northern countries and the dry season of the 
tropics, but a small supply of water is required by 
the soil, because at that time the stems lose but little 
by perspiration, and consequently the roots demand 
but little food ; nevertheless, some terrestrial mois- 
ture is required by plants with perennial stems, even 
in their season of rest, because 34) it is necessary 
that their system should, at that time, be replenished 



114 APPLICATION OF PRINCIPLES. 

with food against the renewal of active vegetation : 
hence, when trees are taken out of the earth in 
autumn, and allowed to remain exposed to a dry air 
all the winter, they either perish, or are greatly enfee- 
bled. If, on the other hand, the soil in which they 
stand is filled with moisture, their system is dis- 
tended with aqueous matter at a time when it cannot 
be decomposed or thrown off, and the plant either 
becomes naturally susceptible of the influence of cold 
in rigorous climates (112), or is driven prematurely 
into growth, when its new parts perish from the unfa- 
vourable state of the air in which they are developed. 
The most suitable condition of the soil, at the period 
of vegetable rest, seem to be that in which no more 
aqueous matter is contained than the results from the 
capillary attraction of the particles. 

Nevertheless, there are exceptions to this, in the 
case of aquatic and marsh plants, whose peculiar con- 
stitution enables them to bear with impunity, during 
winter, an immersion in water ; and in that of many 
kinds of bulbs, which, during their season of rest, are 
exposed to excessive heat. The latter plants are, 
however, constructed in a peculiar manner ; their 
roots are annual, and perish at the same time as the 
leaves, when the absorbent organs are all lost, so that 
the bulb cannot be supposed to require any supply 
of moisture, inasmuch as it possesses no means of 
taken it up, even if it existed in the soil. This will 
be again adverted to in a future chapter. 

It is when plants are in a state of growth that 
an abundant supply of moisture is required in the 



OF THE MOISTURE OF THE SOIL. 115 

earth. As soon as young leaves sprout forth, perspi- 
ration commences (*70), and a powerful absortion 
must take place by the roots ; the younger the leaves 
are, the more rapid their perspiratory action ; their 
whole epidermis must, at that time, be highly sensi- 
ble to the stimulating power of light (66) ; but as 
they grow older their cuticle hardens, the stomates 
(61) become the only apertures through which 
vapour can fly off, and by degrees even these aper- 
tures are either choked up, or have a diminished irri- 
tability. As a general rule, therefore, we are autho- 
rised to conclude that the ground should be abun- 
dantly supplied with moisture when plants first begin 
to grow, and that the quantity should be diminished as 
the organisation of a plant becomes completed. There 
are, however, some especial cases, which appear 
to be exceptional, in consequence of the unnatural 
state in which we require plants to be preserved for 
our own peculiar purposes. One of the effects of an 
excessive supply of moisture is, to keep all the newly 
formed parts of a plant tender and succulent, and 
therefore such a constant supply is desirable when 
the leaves of plants are to be sent to table, as in the 
case of Spinach, Lettuces, and other oleraceous 
annuals. Another effect is, to render all parts natu- 
rally disposed to be succulent, much more so than 
they otherwise would be ; thus we find market-gar- 
gardeners deluging their Strawberry plants with 
water while the fruit is swelling, in order to assist in 
that, to them, important operation. While, however, 
in this case, the size of the fruit is increased by a 



116 APPLICATION OF PRINCIPLES. 

copious supply of water to the earth, its flavour is, in 
proportion, diminished ; for, in consequence of the 
rapidity with which the strawberry ripens, and, per- 
haps, the obstruction of light by its leaves, the excess 
of aqueous matter taken into the system cannot be 
decomposed, and formed into those products which 
give flavour to fruit ; but it must necessarily remain 
in an unaltered condition. 

It is for the reason just given, that the quantity of 
water in the soil should be diminished when succu- 
lent fruit is ripening ; we see this happen in nature, 
all over the world, and there can be no doubt of its 
being of great importance. Not only is the quality 
of such fruit impaired by a wet soil, as has just been 
shown, but because of its low perspiratory power, the 
fruit will burst from excess of moisture, as occurs to 
the plum and grape in wet seasons. The melon, 
although an apparent exception to this rule, is not 
really so ; that fruit acquires its highest excellence in 
countries where its roots are always immersed in water, 
as in the floating islands of Cashmere, the irrigated 
fields of Persia, and the springy river-beds of India. 
But it is to be remembered that the leaves of this 
plant have an enormous perspiratory power, arising 
partly from their large surface, and partly from the 
thinness and consequent permeability of their tissue, 
so that they require a greater supply of fluid than 
most others, and, in the next place, the heat and 
bright light of such countries are capable of decom- 
posing and altering the fluids of the fruit with a 
degree of rapidity and force to which we can here 



OF THE MOISTURE OF THE SOIL. 117 

have no parallel. In this country the melon does not 
succeed if the roots are immersed in water, as I ascer- 
tained some years ago, in the garden of the Horticul- 
tural Society, by repeated experiments. Melons 
were planted in earth placed on a tank of water, into 
which their roots quickly made their way; they 
grew in a curvilinear iron hot-house, and were trained 
near to the glass, and consequently were exposed to 
all the light and heat that can be obtained in this 
country. They grew vigorously and produced their 
fruit, but it was not of such good quality as it would 
have been had the supply of water to the roots been 
less copious. Thus, in the tropics, the quantity of rain 
that falls in a short time is enormous ; and plants are 
forced by it into a rapid and powerful vegetation, 
which is acted upon by a light and temperature 
bright and high in proportion, the result of which is 
the most perfect organization of which the plants are 
susceptible : but, if the same quantity of water were 
given to the same plants at similar periods in this 
country, a disorganisation of their tissue would be 
the result, in consequence of the absence of solar 
light in sufficient quantity. 

The effect of continuing to make plants grow in 
a soil more wet than suits them is well known to be 
not only a production of leaves and ill-formed shoots, 
instead of flowers and fruit, but, if the water is in 
great excess, of a general yellowness of appearance, 
owing, as some chemists think, to the destruction, by 
the water, of a blue matter which, by its mixture 
with yellow, forms the ordinary verdure of vegeta- 



118 APPLICATION OF PRINCIPLES. 

tion. If this condition is prolonged, the vegetable 
tissue enters into a state of decomposition, and death 
ensues. In some cases the joints of the stem sepa- 
rate, in others the plant rots off at the ground, and 
all such results are increased in proportion to the 
weakness of light, and the lowness of temperature. 
De Candolle considers that the collection of stagnant 
water about the neck of plants prevents the free 
access of the oxygen of the air to the roots ; but 
it seems to me that much more mischief is produced 
by the coldness of the soil in which water is allowed 
to accumulate. It seems also probable that the extri- 
cation of carburetted hydrogen gas is one cause 
of the injury sustained by plants whose roots are sur- 
rounded by stagnant water ; but upon this point we 
want much more satisfactory evidence than we yet 
possess. 

It is because of the danger of allowing any accu- 
mulation of water about the roots of plants that 
drainage is so very important. In very bibulous 
soils this contrivance is unnecessary ; but in all 
those which are tenacious, or which, from their low 
situation, do not permit superfluous water to filter 
away freely, such a precaution is indispensable. No 
person has ever seen good fruit produced by trees 
growing in lands imperfectly drained ; and all expe- 
rienced gardeners must be acquainted with cases 
where wet unproductive borders have been rendered 
fruitful by contrivances which are only valuable 
because of their efficiency in regulating the humidity 
of the soil. Mr. Hiver (Gard. Mag., v. 60,) speaks of 



OF THE MOISTURE OF THE SOIL. 119 

the utility of mixing stones in great quantities with 
the soil, "as they prevent the accumulation of water 
in very wet weather, and retain sufficient moisture 
for the purposes of the plant in dry seasons ;" and 
when we hear of such precautions as are detailed 
in the following good account of preparing a Yine 
border, we only learn how important it is to provide 
effectually for the removal of superfluous water from 
around the roots, and how useless a waste of money 
is that which is expended in forming deep rich beds 
of earth. 

" In preparing a Yine border," says Mr. Griffin, of 
Woodhall, a successful grower of grapes, " one foot 
in depth of the mould from the surface is cleared out 
from the whole space ; a main drain is then sunk 
parallel to the house, at the extremity of the border, 
one foot lower than the bottom of the border ; into 
this, smaller drains are carried diagonally from the 
house across the border. The drains are filled with 
stone. The cross drains keep the whole bottom 
quite dry ; but if the subsoil be gravel, chalk, or 
stone, they will not be necessary. The drainage 
being complete, the whole bottom is covered with 
brick, stone, or lime rubbish, about six inches thick, 
and on this is laid the compost for the vines." (Hort, 
Trans, iv., 100.) 

The practice of placing large quantities of pot- 
sherds or broken tiles at the bottom of tubs or pots, 
or other vessels in which plants are rooted, is only 
another exemplification of the great necessity of 
attending to the due humidity of the soil, and to the 



120 APPLICATION OF PRINCIPLES. 

prevention of stagnant water collecting about the 
roots ; and the injury committed by worms, upon the 
roots of plants in pots, is chiefly produced by these 
creatures reducing the earth to a plastic state, and 
dragging it among the potsherds so as to stop up the 
passage between them, and destroy the drainage.* 

One of the means of guarding the earth against an 
access on the one hand, and a loss on the other, of too 
much water, is by paving the ground with tiles or 
stones ; and the advantages of this method have been 
much insisted upon. But it is certain that, in cold 
summers at least, such a pavement prevents the soil 
from acquiring the necessary amount of bottom heat ; 
and it is probable that, what with this effect, and the 
obstruction of a free communication between the at- 
mosphere and the roots of a plant, the practice is disad- 
vantageous rather than the reverse. f 

* [Glazed flower-pots are totally unlit for most plants, except 
with the most careful attention to drainage, and even then they are 
much inferior to common unglazed ones. The latter permit the 
excess of water to escape through their porous sides, which is impos- 
sible in the glazed pot ; in which, if the aperture at the bottom 
become stopped, the earth is sodden with water, the plant suffers 
and soon perishes. A. J. D.] 

f Here, again, it is necessary for the American reader to make 
allowances for the differences of climate. Covering the soil in 
summer, is, in this country, one of the most valuable aids to good 
cultivation ever put in practice. The best mode of doing this is, 
indeed, not by paving, but by what is technically called mulching. 
This consists in spreading over the surface of the ground, so far aa 
the roots of tree or plant extend beneath it, a layer of tan-bark, 
saw-dust, barn-yard litter, straw, salt -hay, sea-weed, or the like, of 
sufficient thickness to maintain, as nearly as possible, an uniform 



OF WATERING. 121 

More commonly recourse is had to the operation of 
simple watering, for the purpose of maintaining the 
earth at a due state of humidity, and to render plants 
more vigorous than they otherwise would be ; an in- 
dispensable operation in hot-houses, but of less moment 
in the open air. It is, indeed, doubtful whether, in the 
latter case, it is not often more productive of disadvan- 
tage than of real service to plants. When plants are 
watered naturally, the whole air is saturated with hu- 
midity at the same time as the soil is penetrated by the 
rain ; and in this case the aqueous particles mingled 
with the earth are very gradually introduced into the 
circulating s} T stem : for the moisture of the air pre- 
vents a rapid perspiration. Not so when plants in the 
open air are artificially watered. This operation is 
usually performed in hot dry weather, and must neces- 
sarily be very limited in its effects ; it can have little if 
any influence upon the atmosphere : then, the parched 
air robs the leaves rapidly of their moisture, so long as 
the latter is abundant ; the roots are suddenly and vio- 
lently excited, and after a short time the exciting 

state of temperature and moisture for the roots. From an experi- 
ence of some years we do not hesitate to say that mulching the sur- 
face of the ground over newly-planted trees is not only far better 
than any after watering — but that — if the layer is thick enough to 
keep the surface cool — it renders watering wholly unnecessary. In 
the case of bearing fruit-trees, especially the more delicate kinds, as 
dwarf pears, apricots, «fcc, mulching not only precludes the necessity 
of stirring the soil, by preventing weeds from growing, but it con- 
duces so much more to the health of the tree, and the size and excel- 
lence of the fruit than any other practice in horticulture, that the 
more intelligent growers in the United States now consider it 
indispensable in this climate. A. J. D. 
6 



122 APPLICATION OF PKIKCIPLES, 

cause is suddenly withdrawn by the momentary supply 
of water being cut off by evaporation, and by filtration 
through the bibulous substances of which soil usually 
consists. Then again, the rapid evaporation from the 
soil in dry weather has the effect of lowering the tem- 
perature of the earth, and this has been before shown 
to be injurious (p. 118); such a lowering, from such a 
cause, does not take place when plants are refreshed 
by showers, because at that time the dampness of the 
air prevents evaporation from the soil just as it prevents 
perspiration from the leaves. Moreover, in stiff soils, 
the dashing of water upon the surface has after a little 
while the effect of "puddling" the ground and render- 
ing it impervious, so that the descent of water to the 
roots is impeded, whether it is communicated artifi- 
cially, or by the fall of rain.* It is, therefore, doubtful 

* [Xo error is more common in this country than surface- 
watering newly transplanted trees ; and we do not hesitate to 
affirm that full one half the failures, in our dry summers, arise 
from this injudicious practice. By pouring water daily on the 
top of the ground, under a powerful sun and strong wind, the sur- 
face becomes so hard that access of the air to the roots is almost 
precluded; and the water rarely penetrates more than a couple 
of inches ; while the operator imagines he is supplying the thirsty 
roots with abundant moisture, he is doing them an injury by the 
application of a very transient stimulus, which is followed by an 
increased sensibility to the drought. In late spring planting, it is 
always preferable to water abundantly in the hole, while planting 
the tree, before filling in the upper layer of soil. This will in 
most cases suffice, until the tree becomes sufficiently established 
by the emission of new rootlets to support itself; and also serves 
to ensure its growth by filling up all the small hollows around the 
lesser fibres. In seasons of continued drought, when it becomes 
absolutely necessary to water flagging trees, two or more inches 



OF WATERING. 123 

whether artificial watering of plants in the open air is 
advantageous, unless in particular cases ; and most as- 
suredly, if it is done at all, it ought to be much more 
copious than is usual. It is chiefly in the case of an- 
nual crops that watering artificially is really impor- 
tant ; and with them, if any means of occasionally de- 
luging ground can be devised, by means of sluices or 
otherwise, in the same way that we water meadows, it 
may be expected to be advantageous.* Mildew, which 
is so often produced by a dry air acting upon a delicate 
surface of vegetable tissue, is completely prevented in 
annuals by very abundant watering, f The ravages 

of the surface soil should always be removed, the trees watered 
copiously, and the earth replaced before the surface dries. This 
will prevent evaporation and encrusting of the ground, and the 
moisture will be retained for a much longer period. A. J. D.] 

* " In the vicinity of Liegen (a town in Nassau), from three to 
five perfect crops of grass are [annually] obtained from one meadow ; 
and this is effected by covering the fields with river-water, which 
is conducted over the meadow in spring by numerous small canals. 
This is found to be of such advantage, that supposing a meadow not 
bo treated to yield 1000 lbs. of hay, then from one thus watered 
4-5000 lbs. are produced. In respect to the cultivation of meadows, 
the country around Liegen is considered to be the best in all Ger- 
many." Liebig, Organ. Chem., p. 105. — G. 

f The mildew which attacks the young fruit of the foreign 
grape, when reared in the open air, is one of the most troublesome 
to the cultivator in this country. An effectual remedy is the flowers 
of sulphur dusted over the bunches with a dredging-box (or the 
solution applied with a syringe), when the grapes are of the size of 
small peas. But the most certain prevention of this, as well as most 
diseases to which plants are subject, consists in keeping the vines in a 
thrifty and vigorous condition. The first crop or two of a young 
thrifty vine is almost invariably fine and free from mildew ; but 
every subsequent year (if the common mode of pruning is followed), 



124 APPLICATION OF PRINCIPLES. 

of the Botrytis effusa, which attacks Spinach; of 
Acrosporium monilioides, which is found on the 
Onion ; and the mildew of the Pea, caused by the ra- 
vages of Erysiphe communis, may all be stopped, or 
prevented, by abundant watering in dry weather. Mr. 
Knight first applied this fact to the securing a late 
crop of peas for the table, in the following manner : — 
The ground is dug in the usual way, and the spaces 
which will be occupied by the future rows are well 
soaked with water. The mould upon each side is 
then collected, so as to form ridges seven or eight inches 
above the previous level of the ground, and these are 
well watered ; after which, the seeds are sowed in single 
rows along the tops of the ridges. The plants very 
soon appear above the soil, and grow with much vigour, 
owing to the great depth of the soil and abundant 
moisture. Water is given rather profusely once in 
every week or nine days, even if the weather proves 
showery ; but, if the ground be thoroughly drenched 
with water by the autumnal rains, no further trouble 
is necessary. Under this mode of management, the 
plants will remain perfectly green and luxuriant till 

as the plant grows older, the proportion of fair fruit is smaller, until 
at last nothing but shrivelled and mildewed bunches are seen. By 
laying down half of the long shoots of each vine annually, thus form- 
ing new plants, and never allowing the same to bear more than two 
vears, a full crop, free from rust or mildew, may be obtained an- 
nually. Even the finer native sorts, as the Isabella, are sometimes 
liable to mildew on old vines: when this occurs, they should be 
headed back, to bring up a supply of young wood, and plentifully 
manured. The young and thrifty shoots will then have sufficient 
vigour to withstand the attacks of mildew, to which the enfeebled 
fruit produced from the old wood is so liable. A. J. D. 



OF ATMOSPHERICAL MOISTURE. 125 

their blossoms and young seed-vessels are destroyed 
by frost, and their produce will retain its proper 
flavour, which is always taken away by mildew. 
(Eort. Trans., ii. 87.) 



CHAPTEE III. 

OF ATMOSPHERICAL MOISTURE AND TEM- 
PERATURE.* 

The constituent parts of the atmosphere that sur- 
rounds us are either the same in different regions, or 
the differences, if any, are not appreciable by chemi- 
cal processes. It is far otherwise as regards temper- 
ature and humidity, which are so intimately con- 
nected that they cannot be considered apart from 
each other. 

From what has been already stated (Book I. Chap. 
IT.)} it is apparent that of the vital functions of 
plants none are more important than those of perspi- 
ration and evaporation ; and that, while a certain 
amount of loss of their fluid particles is necessary, a 
great excess or diminution of the loss must be inju- 
rious. Although the solar rays appear to be the 

* This subject has already been fully treated by Professor Daniell, 
in his excellent paper, "On Climate with regard to Horticulture," 
published in the Transactions of the Horticultural Society, vol. vi. 
p. 1. It is impossible for any one to discuss the same topic without 
profiting largely by this important treatise, which I have very much 
followed in the present chapter. 



126 APPLICATION OF PRINCIPLES. 

immediate cause of perspiration, which proceeds in 
proportion to their intensity (71), yet this action is 
necessarily modified by the state of the medium, that 
is, of the atmosphere which surrounds them : in pro- 
portion to its heat and dryness will their power be 
augmented, and in proportion to its cold and mois- 
ture diminished. The physiological effect of an 
excessive augmentation of perspiration is to dry 
up the juices and to destroy the texture of the leaves; 
on the other hand excessive obstruction of that func- 
tion prevents the decomposition and assimilation 
of the fluids, and the formation of new organised 
matter, as well as of the secretions peculiar to a 
species. A state of the atmosphere, therefore, which 
is most favourable to the maintenance of the perspi- 
ratory action in the most healthy state, is that which 
it must be the business of a gardener to secure by all 
the means in his power. 

Among the hygrometers intended for measuring 
the quantity of elastic vapour in the atmosphere, the 
most convenient for use is that invented by Professor 
Daniell. In this instrument, the amount of moisture 
in a given atmosphere is indicated by what is called 
the dew-point; that is to say, by the point of the 
thermometric scale at which the cold is sufficient 
to cause a deposition of dew; the amount being cal- 
culated by the difference between the natural tempe- 
rature and an artificial temperature created for the 
purpose of determining the point at which the elastic 
vapour of the air is precipitated by cold. " The 
natural scale of the hygrometer," says Mr. Daniell, 



OF ATMOSPHERICAL MOISTURE. 127 

"is included between the points of perfect dryness 
and perfect moisture ; the latter, of course, being that 
state of the atmosphere at which the dew-point coin- 
cides with the temperature of the air. The inter- 
mediate degrees may be ascertained by dividing the 
elasticity of vapour at the temperature of the dew- 
point, by the elasticity of the temperature of the air : 
the quotient will express the proportion of moisture 
actually existing, to the quantity which would be 
required for saturation; for, calling the term of satu- 
ration 1*000, as the elasticity of vapour at the tempe- 
rature of the air is to the elasticity of vapour at the 
temperature of the dew-point, so is the term of satu- 
ration to the actual degree of moisture." 

By means of this and similar contrivances,* we are 
at all times able to ascertain exactly the quantity of 
water that exists in an elastic state in the air. 

In this country, the changes of moisture are said to 
extend from 1*000, or saturation, to *389, or even 
so low as *120, under a south wall, for a short space 
of time ; " a state of dryness which is certainly not 
surpassed by an African harmattan," but one which 
produces less disastrous consequences, because it is 
accompanied by a far lower temperature and a weaker 
solar radiation. The mean degree of moisture of the 
air near London has been found by Mr. Thompson to 
be -897, on an average of ten years, while the mean 

* Other hygrometers have been invented to answer the same 
end ; but, as Mr. DanielFs is that most eligible in this country, I 
have thought it more convenient to confine mj -observations 
to it 



128 APPLICATION OF PRINCIPLES. 

temperature is 50*62 : * in other parts of the world 
it is very different ; and the amount of those differ- 
ences, together with the means of imitating them arti- 
ficially, constitutes one of the most delicate and diffi- 
cult parts of the gardener's art. All that relates 
to this subject, however, to be treated usefully, must 
be considered in a very special way, and in such 
detail as can only be expected in a separate work 
upon the subject. An idea of the difference between 
the atmospherical moisture of London and that of 
other parts of the world ma} 7 , however, be collected 
from the following table showing the amount of rain 
that falls in a few different countries : 

Inches per Annum. 

London 24 '01 Average of 10 years. 

St. Petersburgh .... 16* 

Algiers 27* 

Fattehpur (East Indies) . 85*94 Average of 4 yeara, 

Madeira 81 • 

Sagar (East Indies) . . . from 31 15 to 64*76 

Bahamas 54*99* 

Calcutta from 59*83 to 81* 

Ceylon 843 

Macao ....... from 48*8 to 107*8 

Equator 96* 

Coast of Malabar . . . . 123*50 Average of 14 year*. 

Grenada 126* 

Leogane, St. Domingo . . 150* 

Bengal, 20 to 22 inches in a single month. 

Bombay, 32 inches in 12 days. 

Tavoy, 203 *5 inches in six months ; as much as 
8*5 in a day (July 31, 1831).+ 

* See the various meteorological journals published by the Horti- 
cultural Society, in their Transactions, from the year 1826 inclusive, 
f [The average fall of rain (and snow) in the State of New York, 



OF ATMOSPHERICAL MOISTURE. 129 

We possess, to a certain extent, the power of modi- 
fying the moisture of the air even in the open air, 
and have almost complete control over that of glazed 
honses. 

It is found by experience that the effect of wind is 
to increase the dryness of the air, and, consequently, 
the perspiration of vegetable surfaces. "Evapora- 
tion," says Mr. Daniell, "increases in a prodigiously 
rapid ratio with the velocity of the wind ; and any- 
thing which retards the motion of the latter is very 
efficacious in diminishing the amount of the former. 
The same surface which, in a calm state of the air, 
would exhale 100 parts of moisture, would yield 125 
in a moderate breeze, and 150 in a high wind." 
Hence the great importance, in gardens, of walls, and 
screens, which break the wind, and keep the air in 
repose in their vicinity. The difference between the 
effect of a given amount of cold upon the blossoms 
of exposed fruit trees, and those of the same species 
trained upon walls, is well known ; and appears to be 
owing to this circumstance, much more than to any 
difference of temperature in the two situations.* 

for 14 years (1826-1839 inclusive,) as deduced from observations 
made under the direction of the Regents of the University, and col- 
lected in their Report presented March, 1840, is 84*40 inches. The 
highest average (from 54 stations) for any single year is 44*40 (A. D. 
1827) ; the lowest (for 1839) 32*10 inches.] 

* This has been illustrated by Mr. Howard, in the results of 
some interesting experiments made by him on the annual amount of 
evaporation. During three years, in which the evaporating gauge 
was placed forty-three feet from the ground, the annual average 
result was 3r85 inches; during other three years, when the instru- 
ment was lower and less exposed, the average was 33*37 inches ; and 

6* 



130 APPLICATION OF PKLNCIPLES. 

It is to be remarked that the easterly winds are, in 
this country, both the coldest and the driest. Mr. 
Daniell tells us that the " moisture of the air flowing 
from any point between N. E. and s. E. inclusive, is, 
to that of the air from the other quarters of the com- 
pass, in the proportion of '814 to '907, upon an ave- 
rage of the whole year;" and Mr. Thompson has 
found the hygrometer to indicate not uncommonly 
from 20° to 30° of dryness, during the long pre- 
valence of the north-easterly winds in spring. At 
the same time, the air is very cold, the effect of which 
is to cause the sap- vessels of the stem to contract, and 
refuse to convey their fluid ; so that the blossoms of 
fruit trees in a north-east wind, while they are robbed 
of their fluid contents by evaporation, can get no as- 
sistance from the roots through the stem, and neces- 
sarily perish. I find, however, from Mr. Thompson's 
observations, that the greatest dryness we experience 
in this climate is, not when the wind is in the east, 
but when it is in the south. For example : in nine 
years, between 1826 and 1831, the four driest days 
were, in the year 1831, in June, when it was 33° on 
the 1st, 35° on the 2d, and 31° od the 21st ; on the 
1st of June, 1833, it was 30°, and always with a south 
wind; and, during the whole of those nine years, 
there was but one other day on which the dryness 
was found as high as 30°, namely on the 10th of April, 
1831, with a north-east wind. The duration of dry- 
when the gauge was upon or near the ground the annual average 
was only 20-28 inches, or little more than half the amount evapo- 
rated in a free and elevated exposure. 



OF ATMOSPHERICAL JIOISTU&E. 131 

Etess, with a south wind, was, however, very short, 
not exceeding one or at most two days, and was in- 
variably accompanied with great heat and followed 
by heavy rain .; while the north-easters last for weeks, 
without rain and with a comparatively low tempera- 
ture. The following statement by Mr. Thompson 
puts this in a clear light. There occurred between 
1826 and 1834 inclusive- 
Wind North . . 7 days* above 20° of dryness. 
K East . C 39 da da 

E&st 114 < 48 da da 

S. East . I 21 do. da 

South . 35 do. da 

S. West . 30 da da 

West „ 35 do. da 

K West , 22 do. da 

These facts sufficiently explain the fatal effects of 
certain winds upon vegetation, the small comparative 
value in this country of walls with north and east 
aspects, and the general want of success that attends 
late spring planting. Here, also, we in part discover 
an explanation of the utility of shades interposed be- 
tween the sun and plants newly committed to the 
earth * they not only cut off the solar rays, but also 
intercept currents of air, and thus diminish the 
amount of perspiration by two opposite methods. 

The following table, for which I am again indebted 
to Mr. Thompson, will be found to show that the 
average degree of dryness, in the middle of the day, 
throughout the year, is, with a 



132 AMPLICATION OF FBINCIPLE& 

Degrees Amount 

of Dryness. uf Moisture. 

North wind . . . 6'55° . . 816 
North-east ... 7-30 194 

East . . 6-20 825 

Average, with wind from the ) fi , fi _ ft .. 

three coldest points ) 

South wind 
South-west 

West 

Average, with wind from the ) -,. . 
three warmest points ) 



4-23 


877 


4-70 


859 


6-20 


733 



OF ATMOSPHERICAL MOISTURE. 



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OF ATMOSPHERICAL TEMPERATURE. 135 

As to temperature in the open air, unconnected 
with atmospherical humidity, there seems to be no 
means of regulating or modifying it to any consider- 
able extent. In some respects, however, we have 
even this powerful agent under our control ; but, in 
order to exercise such control, it is necessary to un- 
derstand correctly the theory of what is called radia- 
tion, which cannot be better explained than in the 
words of Mr. Daniell. " The power of emitting heat 
in straight lines in every direction, independently pf 
contact, may be regarded as a property common to 
all matter; but differing in degree in different kinds 
of matter. Coexisting with it, in the same degrees, 
may be regarded the power of absorbing heat so 
emitted from other bodies. Polished metals and the 
fibres of vegetables may be considered as placed at 
the two extremities of the scale upon which these pro- 
perties in different substances may be measured. If 
a body be so situated that it may receive just as 
much radiant heat as itself projects, its temperature 
remains the same ; if the surrounding bodies emit 
heat of greater intensity than the same body, its tem- 
perature rises, till the quantity which it receives ex- 
actly balances its expenditure, at which point it again 
becomes stationary ; and if the power of radiation be 
exerted under circumstances which prevent a return, 
the temperature of the body declines. Thus, if a 
thermometer be placed in the focus of a concave me- 
tallic mirror, and turned towards any portion of the 
sky, at any period of the day, it will fall many de- 
grees below the temperature of another thermometer 



136 APPLICATION OF PRINCIPLES. 

placed near it, out of the mirror ; trie power of radia- 
tion is exerted in both, thermometers, but to the first 
all return of radiant heat is cut off, while the other 
receives as much from the surrounding bodies, as it- 
self projects. This interchange amongst bodies takes 
place in transparent media as well as in vacuo ; but 
in the former case, the effect is modified by the 
equalising power of the medium. 

u Any portion of the surface of the globe which is 
fully turned towards the sun receives more radiant 
heat than it projects, and becomes heated ; but when, 
by the revolution of the axis, this portion is turned 
from the source of heat, the radiation into space still 
continues, and, being uncompensated, the temperature 
declines. In consequence of the different degrees in 
which different bodies possess this power of radiation, 
two contiguous portions of the system of the earth 
will become of different temperatures ; and if on a 
clear night we place a thermometer upon a grass-plat, 
and another upon a gravel walk or the bare soil, we 
shall find the temperature of the former many degrees 
below that of the latter. The fibrous texture of the 
grass is favourable to the emission of the heat, but 
the dense surface of the gravel seems to retain and 
fix it. But this unequal effect will only be perceived 
when the atmosphere is unclouded, and a free passage 
is open into space ; for even a light mist will arrest 
the radiant matter in its course, and return as much 
to the radiating body as it emits. The intervention 
of more substantial obstacles will of course equally 
prevent the result, and the balance of temperature 



OF ATMOSPHERICAL TEMPERATURE. 137 

will not be disturbed in any substance which is not 
placed in the clear aspect of the sky. A portion of 
a grass-plat under the protection of a tree or hedge, 
will generally be found, on a clear night, to be eight 
or ten degrees warmer than surrounding unsheltered 
parts ; and it is well known to gardeners, that less 
dew and frost are to be found in such situations, than 
in those which are wholly exposed/' (Hort. Trans., 
vi. 8.) 

These laws plainly direct us to the means we are 
to employ to moderate atmospherical temperature. 
A screen, of whatever kind, interposed between the 
sun and a plant, intercepts the radiant heat of the 
sun, and returns it into space ; and thus, in addition 
to the diminution of perspiration by the removal of a 
part of the stimulus that causes it, actually tends to 
lower the temperature that surrounds the plant. In 
like manner, the interposition of a screen, however 
slight, between a plant and the sky, intercepts the 
radiant heat of the earth ; and, instead of allowing it 
to pass off into space, returns it to the ground, the 
temperature of which is maintained at a higher point 
than it otherwise would be. Hence it is that plants 
growing below the deep projecting eaves of houses, or 
guarded by a mere coping of thatched hurdles, suffer 
less in winter than if they were fully exposed to the 
sky. 

It is also obvious from what has been stated, that 
plants growing upon grass will be exposed to a greater 
degree of cold in winter than such as grow upon 
gravel : but it does not therefore follow that hard 



138 APPLICATION OF PRINCIPLES. 

gravel is, with respect to vegetation, a better coating 
for the surface of the ground than turf; it has its dis- 
advantages as well as its advantages, and the former 
probably outweigh the latter. In superior heating 
power is its only advantage ; the objections to it are, 
its dryness in summer, and its comparative imper- 
meability to rain, so that it causes the force of per- 
spiration to be inversely as the absorbing power of 
the roots. 

It is well known that blackened surfaces absorb 
heat much more than those of any other colour ; and 
it has been expected that the effect of blackening gar- 
den walls, on which fruit trees are trained, would be 
to accelerate the maturation of the fruit ; but notwith- 
standing a few cases of apparent advantage, one of 
which, of the Vine, is mentioned in the Horticultural 
Transactions, vol. iii. p. 330, this has been, in general, 
found either not to happen at all, or to so small an 
extent as not to be worth the trouble, It is true, that 
so long as the wall is so little covered by the 
branches and leaves of a plant, the absorbent power 
of the blackened surface is brought into play ; but 
this effect is lost as soon as the well becomes covered 
with foliage. In the early spring, however, before 
the leaves appear, the flowers are brought rather more 
forward than would otherwise be the case; and in the 
autumn the wood certainly becomes more completely 
ripened, a result of infinite consequence in the north- 
ern parts of the country. 

It is rather to a judicious choice of soil and situa- 
tion that the gardener must look for the means of 



OF ATMOSPHERICAL TEMPERATURE. 189 

softening the rigour of climate. Wet tenacious soils 
are found the most difficult to heat or to drain, and 
they will, therefore, be the most unfavourable to the 
operations of the gardener ; extremely light sandy 
soils, on the other hand, part with their moisture so 
rapidly, and absorb so much heat, that they are 
equally unfavourable ; and it is the light loamy soils, 
which are intermediate between the two extremes, 
that, as is well known, form the best soil for a gar- 
den. Situation is, however, of much more conse- 
quence than soil, for the latter may be changed or 
improved, but a bad (that is, cold) situation is incur- 
able. Cold air is heavier than warm air, and, conse- 
quently, the stratum of the atmosphere next the soil 
will be in general colder than those above it. When, 
therefore, a garden is placed upon the level ground of 
the bottom of a valley, whatever cold air is formed upon 
its surface remains there, and surrounds the herbage ; 
and, moreover, the cold air that is formed upon the 
sides of low hills rolls down into the valley as quick- 
ly as it is formed. Hence the fact which to many 
seems surprising, that what are called sheltered places 
are, in spring and autumn, the coldest. We all know 
that the Dahlias, Potatoes, and Kidneybeans of the 
sheltered gardens in the valley of the Thames, are 
killed in the autumn by frosts whose effects are un- 
felt on the low hills of Surrey and Middlesex.* Mr. 

* [A contrary effect is experienced in the valleys of our large 
rivers and lakes in the United States. On the banks of the Hudson 
a margin of land from half a mile to a mile in width on each side is 
very effectually protected from the late spring and early autumnal 



140 APPLICATION OF PRINCIPLES. 

Daniell says he has seen a difference of 30°, on the 
same night between two thermometers, placed, the 
one in a valley, and the other on a gentle eminence, 
in favour of the latter. Hence, he justly observes, 
the advantages of placing a garden upon a gentle 
slope must be apparent ; "a running stream at its foot 
would secure the further benefit of a contiguous sur- 
face not liable to refrigeration, and would prevent any 
injurious stagnation of the air." 

In addition to this, it has been said that, to obtain 
the most favourable conditions of climate in this 
country, a garden should have a south-eastern expo- 
sure. This, however, has been recommended, I 
think, without full consideration. It is true that in 
such an exposure the early sunbeams will be re- 
ceived ; but, on the other hand, vegetation there 
would be exposed to several unfavourable actions. 
There would be little protection from easterly 
winds, which, whether south-east or north-east, are 
the coldest and driest that blow ; in the next place 
an exposure to the first sun of the morning, is very 
prejudicial to garden productions that have been 
frozen by the radiation of the night ; it produces 

frosts ; "while beyond that limit vegetation is blackened by them. 
In autumn the warm vapour which rises on a cold night from so 
large a surface probably protects the adjacent shores : and even 
when moderate frosts actually occur, the morning fog, which lasts 
an hour or two, by softening the sun's rays and causing a gradual 
thmv, often prevents any injurious result to vegetation. Some of 
our large inland lakes, the surfaces of which ar* never frozen, have 
a decided effect upon the local climate, rendering it much more mild 
than it other wiee would be. — A J. D.] 



OF ATMOSPHERICAL TEMPERATURE. 141 

a sudden thaw, which, as gardeners well know,* 
causes the death of plants which, if slowly thawed, 
would sustain no inconvenience from the low temper- 
ature to which they had been exposed. f It is proba- 
ble, as I have elsewhere endeavoured to show, that 
this singular effect may be accounted for as follows : — 
" In such cases, it may be supposed that the air, 
forced into parts not intended to contain it, is 
expanded violently, and thus increases the disturb- 

* See Hort. Trans., iii. 43. 

■j- [In the northern and eastern sections of the Union many beau- 
tiful shrubs and plants, which are the ornaments of our gardens in 
summer, but perish if exposed to the rigorous cold of winter, are 
easily preserved upon this principle. The first impulse of the 
novice in gardening is to place such half-hardy plants (as the more 
delicate China Roses, Carnations, <fcc.) in some warm sheltered spot, 
open to the genial rays of the sun in winter : a practice invariably 
followed by their destruction. Our sun, even in mid-winter, often 
shines with great brightness, and the thawing and distension of the 
tissue of tender plants which therefore follows causes certain death. 
If, on the contrary, the same species are placed in a cool shaded 
aspect, or, what is preferable, if they are shielded from the sun by 
a loose covering of straw, mats, or even boards, and thus kept from 
thawing except in the most gradual manner, they will be found to 
have sustained no injury whatever. We have seen a large num- 
ber of the choicest Camellias preserved without any artificial heat 
through a cold winter, when the mercury ranged below zero for seve- 
ral weeks, simply by covering them with a common glazed frame, 
well clothed with mats to exclude the direct rays of the sun, or pre- 
vent sudden variations of temperature. For the same reason, or- 
chards of Peach trees in the middle States, on the cold north sides 
of hills, are often more vigorous and of greater longevity than those 
in a full southern aspect : the heat of our summers being sufficient to 
ripen their fruit and wood in such situations, while they are thus 
secured from the evils of great and sudden changes of temperature 
in winter. A. J. D.] 



142 APPLICATION OF PRINCIPLES. 

ance already produced by its expulsion from the 
proper air cavities ; while, on the other hand, when 
the thaw is gradual, the air may retreat by degrees 
from its new situation without producing additional 
derangement of the tissue. It is also possible that 
leaves from which their natural air has been expelled 
by the act of freezing, may, from that circumstance, 
have their tissue too little protected from the evapo- 
rating force of the solar rays, which, we know, pro- 
duce a specific stimulus of a powerful kind upon those 
organs." (Hort. Trans., n. s., ii. 305.) 

In our glazed houses, we have full control over the 
state of the atmosphere, as regards both its moisture 
and temperature, by means familiar to every gar- 
dener ; but the manner of applying those means, and 
the causes that oppose their action, deserve to be the 
subject of inquiry. 

It will have been seen, from what has been already 
stated upon that subject, that in general, in warm 
countries, the air is occasionally at least, if not per- 
manently, filled with vapour to a much greater extent 
than in northern latitudes,* and, as in our glazed 
houses we cultivate exclusively the natives of warm 
countries, it is also obvious that, as a general rule, the 
air of such houses requires, at certain periods, to be 
damper than that of the external air. Those periods 

* " Captain Sabine, in his meteorological researches between the 
tropics, rarely found at the hottest period of the day so great a dif- 
ference as 10° between the temperature of the air and the dew- 
point: making the degree of saturation about -730, but most fre- 
quently 5° or '850 ; and the mean saturation of the air could not 
haye exceeded -910." (Daniell.) 



OF ATMOSPHERICAL TEMPERATURE. 143 

arc when vegetation is most active. On the other hand 
countries nearer the equator are subject to seasons 
of dryness, the continuance of which is often much 
greater than anything we know of here in the open 
air, and consequently artificial means must also be 
adopted to bring about, in glazed houses, that state 
of things at particular periods; namely, those of the 
repose of plants. These facts afford abundant proof 
of the necessity of regulating the moisture of the 
atmosphere with due precision. 

By throwing water upon the pavement of glass 
houses, by means of open tanks of water, by reser 
voirs placed upon them, by syringing, and by other 
contrivances,* the quantity of water in the air may 
be easily increased, even up to the state of saturation. 
But there are some circumstances, easily overlooked, 
which interfere very seriously with this power, and 
which, it may be conceived, may reduce it very much 
below the expectations of the cultivator. 

The most unsuspected of these is the destruction 
of aqueous vapour, by the hot, dry, absorbent surface 
of flues. The advantages derived from hot- water 
pipes, or steam pipes, over brick flues, are so well 
known, as not to require any evidence to prove the 
fact. Gardeners explain the difference in the action 
of the two, by saying that the dry heat produced by 
hot-water pipes is siueeter than that given off by flues ; 
which is not a very intelligible expression. The fact 

* A discharge of steam into a glazed house has occasionally been 
employed ; but the method requires much attention on the part of 
the operator, and seems inferior to other contrivances. 



144 APPLICATION OF PRINCIPLES. 

is, that the air of houses heated by flues is, under 
equal circumstances, much drier than that where hot- 
water pipes are employed ; because the soft-burnt clay 
of the brick flues robs the air of its moisture, while 
the unabsorbent surface of iron pipes abstracts 
nothing. 

Another source of dryness is the coldness of the 
glass roof, especially in cold weather, when its tem- 
perature is lowered by the external air, in conse- 
quence of which the moisture of the artificial atmo- 
sphere is precipitated upon the inside of the glass, 
whence it runs down in the form of " drip." Mr. 
Daniell observes that the glass of a hot-house, at 
night, cannot exceed the mean of the external and 
internal air ; and, taking them at 80° and 40°, 20 
degrees of dryness are kept up in the interior, or a 
degree of saturation not exceeding '528. To this, in 
a clear night, we may add at least 6° for the effects 
of radiation, to which the glass is particularly 
exposed, which will reduce the saturation to "424; 
and this is a degree of drought which must be 
very prejudicial. It will be allowed that this is not 
an extreme case, and much more favourable than 
must frequently occur during the winter season. 
Some idea, he adds, may be formed of the prodi- 
giously increased drain upon the functions of a plant, 
arising from an increase of dryness in the air, from 
the following consideration : — If we suppose the 
amount of its perspiration, in a given time, to be 57 
grains, the temperature of the air being 75° and the 
dew-point 70°, or the saturation of the air being - 849, 



OF ATMOSPHERICAL TEMPERATURE. 145 

the amount would be increased to 120 grains in the 
same time, if the dew-point were to remain station- 
ary, and the temperature were to rise to 80° ; or, in 
other words, if the saturation of the air were to fall 
to -726. (Rort. Trans, vi. 20.) It is well known that 
the effect of maintaining a very high temperature in 
hot-houses at night, during winter, is frequently 
to cause the leaves to wither and turn brown, as if 
scorched or burnt ; and this is apparently owing to 
the dryness of the air, in consequence of the above 
causes. 

It is evident that the mode of preventing this dry- 
ing of the air by the cold surface of a glass roof will 
be, either by raising the temperature of the glass, 
which can only be effected by drawing a covering of 
some kind over our houses at night, so as to intercept 
radiation, or by double glass sashes ; or else by 
keeping the temperature of the air of the house as 
low as possible, consistently with the safety of the 
plants, and so diminishing the difference between the 
temperature of the external and internal air. 

A bad system of ventilation is another cause of the 
loss of vapour in the atmosphere of glazed houses, 
to which reference will be made in the succeeding 
chapter. 

It is, in all appearance, to the attention that, since 
the appearance of Mr. Daniell's paper, in 1824, upon 
this subject, has been paid to the atmospherical mois- 
ture o£ glazed houses, that the great superiority of 
modern gardeners over those of the last generation is 
mainly to be ascribed ; there are, however, traces of 
7 " 



146 APPLICATION OF PKINCIPLES, 

the practice at a much earlier period, although, from 
not understanding the theory of the practice, no 
general improvement took place. In the year 1816, 
an account was laid before the Horticultural Society 
of a very successful mode of forcing grapes and nec- 
tarines, as practised by Mr. French, an Essex farmer, 
with very rude materials, and under unfavourable 
circumstances. It is not a little remarkable, that, 
although Mr. French himself correctly referred his 
success to the skilful management of the atmospheri- 
cal moisture of his forcing-houses, the subject was so 
little understood at that time, that the author of the 
account not only shrank from adopting the opinion, 
but evidently, from the manner in which he speaks 
of Mr. French's explanation, had no idea of its just- 
ness. The method itself is sufficiently remarkable to 
deserve being extracted. 

" About the beginning of March, Mr. French com- 
mences his forcing, by introducing a quantity of new 
long dung, taken from under the cow-cribs in his 
straw yard ; being principally, if not entirely, cow 
dung, which is laid upon the floor of his house, 
extending entirely from end to end, and in width 
about six or seven feet, leaving only a pathway 
between it and the back wall of the house. The dung 
being all new at the beginning, a profuse steam arises 
with the first heat, which, in this stage of the process, 
is found to be beneficial in destroying the ova of 
insects, as well as transfusing a wholesome moisture 
over the yet leafless branches; but which would 
prove injurious, if permitted to rise in so great a 



OF ATMOSPHERICAL TEMPERATURE. 147 

quantity when the leaves have pushed forth. In a 
few days, the violence of the steam abates as the buds 
open, and in the course of a fortnight the heat begins 
to diminish ; it then becomes necessary to carry in a 
small addition of fresh dung, laying it in the bottom, 
and covering it over with the old dung fresh forked 
up : this produces a renovated heat, and a moderate 
exhalation of moist vapour. In this manner the 
heat is kept up throughout the season, the fresh sup- 
ply of dung being constantly laid at the bottom in 
order to smother the steam, or rather to moderate the 
quantity of exhalation ; for it must always be remem- 
bered, that Mr. French attaches great virtue to the 
supply of a reasonable portion of the vapour. The 
quantity of new dung to be introduced at each turn- 
ing must be regulated by the greater or smaller 
degree of heat that is found in the house, as the sea- 
son or other circumstances appear to require it. The 
temperature kept up is pretty regular, being from 65 
to 70 degrees." (Rort Trans., i. 245.) 

In this case, which attracted much attention at the 
time, it is evident that the success of the practice 
arose principally out of two circumstances ; firstly, 
the moisture of the atmosphere was skilfully main- 
tained in due proportion to the temperature ; and, 
secondly, a suitable amount of bottom heat was 
secured. This is, as will be elsewhere remarked, the 
principal cause of the advantages found to attend the 
Dutch mode of forcing. The reporter upon Mr. 
French's practice speaks with surprise of the rudeness 
of the roof of his forcing-houses, and of the nume- 



148 APPLICATION OF PRINCIPLES. 

rous openings into the air through the laps of the 
glass and the joints of the sashes ; but these were 
points of no importance under the mode of manage- 
ment adopted. 

The impossibility of preserving any plants except 
succulents, in a healthy state, for any long period, in 
a sitting-room, is evidently owing to the impracticabi- 
lity of maintaining the atmosphere of such a situation 
in a state of sufficient dampness.* 

An excess of dampness is indispensable to plants, 
in a state of rapid growth, partly because it prevents 
the action of perspiration becoming too violent, and 
partly because under such circumstances a considera- 
ble quantity of aqueous food is absorbed from the 
atmosphere, in addition to that obtained by the 
roots. 

But it is essential to observe that, when not in 
a state of rapid growth, a large amount of moisture in 
the air will be prejudicial rather than advantageous to 

* And the success of those who do, in spite of the adverse circum- 
stances, succeed in raising fine plants in sitting-rooms, will usually 
be found to be owing to their taking great pains to keep the leaves 
in a healthy condition by frequently syringing or washing them 
with a sponge. One of the most successful parlor-plant amateurs 
we ever knew, gave her plants " a bath," as she called it, twice a 
week. Removing them into a large closet and laying them on their 
sides in a flat tub, she cleaned every pore of the upper and under 
sides of the leaves by a very severe syringing with warm water. 
The plants gained health, not only by the cleansing and the absorp- 
tion of moisture, but by the motion of the stems and branches caused 
by dashing water on them from the syringe, which in a good degree 
compensated for the absence of wind-motion, 60 beneficial to the 
growth of all trees and plants in the open air. A. J. D. 



OF ATMOSPHERICAL TEMPERATURE. 149 

a plant ; if the temperature is at the same time high, 
excitability will remain in a state of continued action, 
and that rest which is necessary (113) will be with- 
held, the result of which will be an eventual destruc- 
tion of the vital energies. But, on the other hand, if 
the temperature is kept low while the amount of 
atmospherical moisture is considerable, the latter is 
absorbed, without its being possible for the plant to 
decompose it ; the system then becomes, in the 
■younger and more absorbent parts, distended with 
water, and decomposition takes place, followed by 
the appearance of a crop of microscopical fungi ; in 
short, that appearance presents itself which is techni- 
cally called " damping off." 

The skilful balancing of the temperature and mois- 
ture of the air, in cultivating different kinds of plants, 
and the just adaptation of them to the various seasons 
of growth, constitute the most complicated and diffi- 
cult part of a gardener's art. There is some danger 
in laying down any general rules with respect to this 
subject, so much depends upon the peculiar habits of 
species, of which the modifications are endless. It 
may, however, I think, be safely stated, that the fol- 
lowing rules deserve especial attention : — 

1. Most moisture in the air is demanded by plants 
when they first begin to grow, and least when their 
periodical growth is completed. 

2. The quantity of atmospheric moisture required 
by plants is, cceteris paribus, in inverse proportion to 
the distance from the equator of the countries which 
they naturally inhabit. 



150 APPLICATION OF PEINCIPLES. 

3. Plants with annual stems require more than 
those with ligneous stems. 

4. The amount of moisture in the air most suitable 
to plants at rest is in inverse proportion to the quan- 
tity of aqueous matter they at that time contain. 
(Hence the dryness of the air required by succulent 
plants when at rest.) 



CHAPTEE IV. 

OF VENTILATION. 

By far the larger number of gardeners attach great 
importance to preserving the power of ventilating 
their houses abundantly, without perhaps sufficiently 
considering the nature of the plants they have to ma- 
nage ; and, as has been justly enough said, by sup- 
posing that plants require to be treated like man 
himself, they consult their own feelings rather than 
the principles of vegetable growth. There can be no 
doubt, however, that -the effect of excessive ventila- 
tion is more frequently injurious than advantageous ; 
and that many houses, particularly hot-houses, would 
be more skilfully managed, if the power of ventilation 
possessed by the gardener were much diminished. 

Animals require a continual renovation of the air 
that surrounds them, because they speedily render it 
impure by the carbonic acid given off, and the oxygen 



OF VENTILATION. 151 

abstracted by animal respiration. But the reverse is 
what happens to plants ; they exhale oxygen during 
the day, and inhale the carbonic acid of the atmo- 
sphere, thus depriving the latter of that which would 
render it unfit for the sustenance of the higher orders 
of the animal kingdom ; and, considering the manner 
in which glass houses of all kinds are constructed, 
the buoyancy of the air in all heated houses, would 
enable it to escape in sufficient quantity to renew it- 
self as quickly as can be necessary for the main- 
tenance of the healthy action of the organs of vege- 
table respiration. It, therefore, is improbable that 
the ventilation of houses in which plants grow is 
necessary to them, so far as respiration is concerned. 
Indeed, Mr, Ward has proved that many plants will 
grow better in confined air, than in that which is often 
changed. By placing various kinds of plants in cases, 
made, not indeed air-tight, for that is impossible with 
such means as can be applied to the construction of a 
glass house, but so as to exclude as much as possible 
the admission of the external air, supplying them 
with a due quantity of water, and exposing them 
fully to light, he has shown the possibility of culti- 
vating them without ventilation, with much more 
success than usually attends ordinary glass-house 
management. 

In forcing-houses, in particular, it will be evident 
from what is about to follow, that ventilation, under 
ordinary circumstances, in the early spring, must be 
productive of injury rather than benefit. Many gar- 
deners now admit air very sparingly to their vineries 



152 APPLICATION OF PRINCIPLES. 

during the time that the leaves are tender, and the 
fruit unformed. Some excellent stoves have no pro- 
vision at all for ventilation ; and we have the direct 
testimony of Mr. Knight as to the disadvantage of the 
practice in many cases to which it has been commonly 
applied. 

It may be objected, says this great horticulturist, 
that plants do not thrive, and that the skins of grapes 
are thick, and other fruits without flavour, in crowd- 
ed forcing-houses : but in these it is probably light, 
rather than a more rapid change of air, that is want- 
ing ; for, in a forcing-house which I have long de- 
voted almost exclusively to experiments, I employ 
very little fire heat, and never give air till my grapes 
are nearly ripe, in the hottest and brightest weather, 
further than is just necessary to prevent the leaves 
being destroyed by excess of heat. Yet this mode of 
treatment does not at all lessen the flavour of the 
fruit, nor render the skins of the grapes thick ; on 
the contrary, their skins are always most remarkably 
thin, and very similar to those of grapes which have 
ripened in the open air. (Hort Trans., ii. 225.) 

While, however, the natural atmosphere cannot be 
supposed to require changing in order to adapt it to 
the respiration of plants, it is to be borne in mind that 
the air of houses artificially heated may be rendered 
impure by the means employed to produce heat. 
Sulphurous acid gas escapes from brick flues, am- 
moniacal vapour from fermenting manure, and there 
may be many unsuspected sources of the introduction 
of vaporous impurities ; an inconceivably minute 



OF VENTILATION. 168 

quantity of which is enough to deteriorate the air, so 
far as vegetation is concerned. Drs. Turner and 
Christison found that to^oo of sulphurous acid gas 
destroyed leaves in forty -eight hours ; and similar 
effects were obtained from hydro-chloric or muriatic 
acid gas, chlorine, ammonia, and other agents, the 
presence of which was perfectly undiscoverable by 
the smell. We also know that the destructive pro- 
perties of air poisoned by corrosive sublimate, per- 
haps by its being dissolved in the vapour of a hot- 
house, are not at all appreciable by the senses. 

Ventilation is necessary, then, not to enable plants 
to exercise their respiratory functions, provided the 
atmosphere is unmixed with accidental impurities ; 
but to carry off noxious vapours generated in the arti- 
ficial atmosphere of a glazed house, and to produce 
dryness, or cold, or both. 

When the external air is admitted into a glazed 
house containing a moist atmosphere, it, under ordi- 
nary circumstances, is much colder than that with 
which it mixes ; the heated damp air rushes out at 
the upper ventilators, and the drier cold air takes its 
place ; the latter rapidly abstracts from the plants 
and the earth, or the vessels in which they grow, a 
part of their moisture, and thus gives a sudden shock 
to their constitution, which cannot fail to be injurious. 
This abstraction of moisture is in proportion to the 
rapidity of the motion of the air. But it is not mere- 
ly dryness that is thus produced, or such a lowering 
of temperature as the thermometer suspended in the 
interior of the house may indicate ; the rapid e vapo- 
7* 



164 APPLICATION OF PRINCIPLES. 

ration that takes place upon the admission of dry air 
produces a degree of cold upon the surface of leaves, 
and of the porous earthen pots in which plants grow, 
of which our instruments give no indication. To 
counteract these mischievous effects, many contri- 
vances have been proposed, in order to ensure the 
introduction of fresh air warm and loaded with mois- 
ture, such as compelling the fresh air to enter a house 
after passing through pipes moderately heated, or 
over hot-water pipes surrounded by a damp atmo- 
sphere, and so on ; the advantages of which, of course, 
depend upon the objects to be attained. 

If ventilation is merely employed for the purpose 
of purifying the air, as is often the case in hot-houses 
and in dung-pits, it should be effected by the intro- 
duction of fresh air, damp and heated. 

If it is only for the purpose of lowering the tempera- 
ture, as in green-houses, or in the midst of summer, the 
external air may be admitted without any precautions. 

But it is very commonly required in the winter, 
for the purpose of drying the air in houses kept at 
that season at a low temperature ; such, for instance, 
as those built for the protection of Heaths, and many 
other Cape and Xew Holland plants : in these cases 
it should be brought into the house as near the tem- 
perature of the house as possible, but on no account 
loaded with moisture. One of the principal reasons 
for drying the air of such houses, is to prevent the 
growth of parasitical fungi, which, in the form of 
mouldiness, constitute what gardeners technically call 
" damp." These jjroductions flourish in damp air at 



OF VENTILATION. 155 

a low temperature, but will not exist either in dry 
cold air or in hot damp air. If the air of cool green- 
houses is allowed to become damp, the fungi imme- 
diately spring up on the surface of any decayed 
leaves, or other matter which may be present, when 
they spread rapidly to the young and tender parts of 
living plants ; and when this happens, they consume 
the juices, choke the respiratory organs, and speedily 
destroy the object they attack. 

Ventilation is also required in the winter in such 
places as dung-pits or frames, especially those in 
which salad, cucumbers, and similar plants are grown. 
In those cases the object is to dry the air, in order 
that the plants may not absorb more aqueous par- 
ticles than they can decompose and assimilate. 
Although plants of this kind will bear a high degree 
of atmospherical moisture in summer, when the days 
are long and the sun bright, and when, consequently, 
(66, 67,) all their digestive energies are in full acti- 
vity, yet they are by no means able to endure the 
same amount in the short dark da3~s of winter, when, 
from the want of light, their powers of decomposition 
or digestion are comparatively feeble. Hence, no 
doubt, the advantage of growing winter cucumbers 
in forcing-houses, instead of dung-frames. 

One of the causes of success in the Dutch method 
of winter forcing is, undoubtedly, their avoiding the 
necessity of winter ventilation, by intercepting the 
excessive vapour that rises from the soil, and which 
would otherwise mix with the air. For this purpose 
they interpose screens of oiled paper between the 



156 APPLICATION OF PRINCIPLES, 

earth and the air of their houses, and in their pits for 
vegetables, they cover the surface of the ground with 
the same oiled paper, by which means vajDour is effec- 
tually intercepted, and the air preserved from exces- 
sive moisture. 

In forcing-houses, ventilation is thought to be 
required at the time when the fruit is ripening, for 
the purpose of increasing the perspiration of the 
plants, and, consequently, of assisting in the elabora- 
tion of the secretions to which fruit owes its flavour ; 
but, even for this, its utility is perhaps overrated, 
and it is quite certain that it may be easily carried to 
excess; for if it is so powerful as to injure the leaves 
by over-drying the air, an effect the reverse of what 
was intended will be produced ; that is to say, the 
quality of the fruit will be deteriorated (64, 75). 
Upon this subject Mr. Knight has made the following 
observations : — "A less humid atmosphere is more 
advantageous to fruits of all kinds, when the period 
of their maturity approaches, than in the earlier 
stages of their growth ; and such an increase of ven- 
tilation at this period, as will give the requisite 
degree of dryness to the air within the house, is 
highly beneficial, provided it be not increased to such 
an extent as to reduce the temperature of the house 
much below the degree in which the fruit had pre- 
viously grown, and thus retard its progress to matu- 
rity. The good effect of opening a peach -house, by 
taking off the lights of its roof during the period of 
the last swelling of the fruit, appears to have led 
many gardeners to overrate greatly the beneficial 



OF VENTILATION. 157 

influence of a free current of air upon ripening fruits ; 
for I have never found ventilation to give the proper 
flavour or colour to a peach, unless that fruit was, at 
the same time, exposed to the sun without the inter- 
vention of glass ; and the most excellent peaches 
I have ever been able to raise were obtained under 
circumstances where change of air was as much as 
possible prevented, consistently with the admission 
of light (without glass), to a single tree." (Hort. Trans., 
ii. 227.) 

It is not improbable that one of the advantages 
of ventilation depends upon a cause but little 
adverted to, but which certainly requires to be well 
considered. 

It v^as an opinion of Mr. Knight, that the motion 
given to plants by wind is beneficial to them by ena- 
bling their fluids to circulate more freely than they 
otherwise would do ; and in a paper printed in the 
Philosophical Transactions for 1803, p. 277, he addu- 
ces, in support of his opinion, many experiments and 
observations; of which the following is sufficiently 
striking : — 

" The effect of motion on the circulation of the sap, 
and the consequent formation of wood, I was best 
able to ascertain by the following expedient. Early 
in the spring of 1801, I selected a number of young 
seedling Apple trees, whose stems were about an inch 
in diameter, and whose height between the roots and 
first branches was between six and seven feet. These 
trees stood about eight feet from each other ; and, of 
course, a free passage for the wind to act on each tree 



158 APPLICATION OF PRINCIPLES. 

was afforded. By means of stakes and bandages of 
hay, not so tightly bound as to impede the progress 
of any fluid within the trees, I nearly deprived the 
roots and lower parts of the stems of several trees of 
all motion, to the height of three feet from the ground, 
leaving the upper part of the stems and branches in 
their natural state. In the succeeding summer, much 
new wood accumulated in the parts which were kept 
in motion by the wind ; but the lower parts of the 
stems and roots increased very little in size. Remov- 
ing the bandages from one of these trees in the fol- 
lowing winter, I fixed a stake in the ground, about 
ten feet distant from the tree, on the east side of it ; 
and I attached the tree to the stake at the height of 
six feet, by means of a slender pole, about twelve 
feet long ; thus leaving the tree at liberty to move 
towards the north and south, or, more properly, in 
the segment of a circle, of which the pole formed a 
radius; but in no other direction. Thus circum- 
stanced, the diameter of the tree from north to south 
in that part of its stem which was most exercised by 
the wind exceeded that in the opposite direction, in 
the following autumn, in the proportion of thirteen to 
eleven." 

Now, if the effect of motion is to increase the 
quantity of wood in a plant, it is evident that ventila- 
tion, which causes motion, must tend to produce a 
healthy action in the plants exposed to it; and such a 
state must also be favourable to the developement of 
all those secretions upon which the organisation of 
flowers, the setting of fruit, and the elaboration of 



OF SEED-SOWING. 159 

colour, odour, flavour, &c, so much depend. Some 
suggestions by Mr. Knight, as to the manner in which 
this result can be artificially produced, will be found 
in the Hort. Trans., vol. iv. p. 2 and 3 : but the sub- 
ject has yet attracted little attention. (See also Hort. 
Trans., new series, i. 34.) 



CHAPTER V. 

OF SEED-SOWING. 

When a seed is committed to the earth, it under- 
goes certain chemical changes (14) before it can de- 
velope new parts and grow. These changes are 
brought about by heat and water, assisted by the ab- 
sence of light. In many seeds the vital principle is 
so strong, that to scatter them upon the soil, and to 
cover them slightly with earth, are sufficient to ensure 
their speedy germination ; but in others the power 
of growth will only manifest itself under very favour- 
able conditions ; it is, therefore, necessary to consider 
well upon what the circumstances most suitable to 
germination depend. 

Moisture is necessary, but not an unlimited quan- 
tity. If seed is thrown into water and exposed to a 
proper temperature, the act of germination will take 
place; but, unless the plant is an aquatic, it will 
speedily perish ; no doubt because its powers of respi- 



160 APPLICATION OF PRINCIPLES. 

ration are impeded, and it is unable to decompose the 
water it absorbs, which collects in its cavities and be- 
comes putrid. There must, therefore, be some 
amount of water, which to the dormant as well as the 
vegetating plant is naturally more suitable than any 
other ; and experience shows that quantity to be just 
so much as the particles of earth can retain around 
and among them by the mere force of attraction. To 
this is to be ascribed the advantage derived from 
those mixtures of peat, loam and sand, which gar- 
deners prefer for their seedlings; the peat and sand 
together keep asunder the particles of loam which 
would otherwise adhere and prevent the percolation 
of water ; the loam retains moisture with force enough 
to prevent its passing off too quickly through the 
wide interstices of sand and peat. If, during the de- 
licate action of germination, the changes that the seed 
undergoes take place without interruption, the young 
plant makes its appearance in a healthy state ; but, 
if by irregular variations of heat, light and moisture, 
the progress of germination is sometimes accelerated 
and sometimes stopped, the fragile machinery upon 
whioh vitality depends may become so much de- 
ranged as to be no longer able to perform its actions, 
and the seed will die. It is for the purpose of secur- 
ing uniformity in these respects, that we employ, in 
delicate cases, the steady heat of a gentle hot-bed, 
shaded ; and, in all cases whatever, the assistance of 
a coating of earth scattered over the seed. 

Under what depth of earth seed should be buried 
must always be judged of by the experience of a gar- 



OF SEED-SOWING. 161 

dener : but it should be obvious that minute seeds, 
whose powers of growth must be feeble in proportion 
to their size, will bear only a very slight covering ; 
while others, of a larger size and more vigour, will 
be capable, when their vital powers are once put in 
action, of upheaving considerable weights of soil. 
As, however, the extent of this power is usually un- 
certain the judicious gardener will take care to em- 
ploy, for a covering, no more earth than is really 
necessary to preserve around his seeds the requisite 
degree of darkness and moisture.-" Hence the com- 
mon practices of sowing small seeds upon the surface 
of the soil, and covering them with a coating of moss, 
which may be removed when the young seedlings 
are found to have established themselves. In other 
cases very minute seeds are mixed with sand before 
they are sown. 

The latter practice is not, however, merely for the 
sake of covering the seed with the smallest possible 
quantity of soil, but has for its object the separation 
of seeds to such a distance, that when they germinate 
they may not choke up each other. If seedlings, like 
other plants, are placed so near together that they 

* It may, perhaps, be as well to notice, in this place, an erroneous 
opinion, not uncommonly entertained, that seeds must be " well" 
buried in order that the young plants, when produced, may have 
" sufficient hold of the ground." The fact is, that a seed, when it 
begins to grow, plunges its roots downwards and throws its stem 
upwards from a common point, which is the seed itself; and, con- 
sequently, all the space that intervenes between the surface of the 
soil and the seed is occupied by the base of the stem, and not by 
roots. 



162 APPLICATION OF PRINCIPLES. 

either exhaust the soil of its organisable matter, or 
overshadow each other so as to hinder the requisite 
quantity of light, some will die in order that the 
remainder may live; and this, in the case of rare 
seeds, should, of course, be guarded against very 
carefully. 

With regard to the temperature to which a seed 
should be subjected, in order to secure its germina- 
tion, this, undoubted^, varies with different species, 
and depends upon their peculiar habits, and the tem- 
perature of the climate of which they are native. So 
far as general rules can be given upon such a subject, 
it may be stated that the temperature of the earth 
most favourable for germination is 50° to 55° for the 
seeds of cold countries, 60° to 65° for those of "green- 
house plants," and 70° to 80° for those of the torrid 
zone. No seed, however, has been known to refuse 
to germinate in the last mentioned temperature, al- 
though those to which such a heat is necessary will 
not, in general, grow in a healthy manner in a lower 
temperature. We have no exact experiments upon 
this subject, except in a few cases recorded by Messrs. 
Edwards and Colin, by whom there is a very valu- 
able set of observations upon the temperatures borne 
by certain agricultural seeds {Annales des Sciences, 
new series, vol. v. p. 5), the result of which may be 
thus stated : — 

At 44-6°, Wheat, Barley, and Rye could germinate. 

95°, in water, for three days, four-fifths of the Wheat and Rye, 

and all the Barley, were killed. 
104°, in sand and earth, the same seeds sustained the tempera- 
ture for a considerable time, without inconvenience. 



OF SEED-SOWING. 163 

At 113°, under the same circumstances most of them perished. 
122°, ditto ditto, all perished. 

But it was found that, for short periods of time, a 
much higher temperature could be borne. 

At 143-6°, in vapour, Wheat, Barley, Kidneybeans, and Flax retain- 
ed their vitality for a quarter of an hour ; but in 27£ mi- 
nutes, the three last died at a temperature of 125 '6°. 

167°, in vapour, they all perished. 

167°, in dry air, they sustained no injury. 

It will be presently seen that some seeds will bear 
a much higher temperature. 

The foregoing observations apply to seeds in a per- 
fect state of health ; when they have become sickly 
or feeble, from age or other causes, some precautions 
become necessary, to which, under other circum- 
stances, no attention requires to be paid. 

When the vital energies of a seed are diminished, 
it does not lose its power of absorbing water, but it is 
less capable of decomposing it (14). The conse- 
quence of this is, that the free water introduced into 
the system collects in the cavities of the seed, and pro- 
duces putrefaction ; the sign of which is the rotting 
of the seeds in the ground. The remedy for this is to 
present water to the seed in such small quantities at a 
time, and so gradually, that no more is absorbed than 
the languid powers of the seed can assimilate ; and to 
increase the quantity only as the dormant powers of 
vegetation are aroused. One of the best means of 
doing this is, to sow seeds in warm soil tolerably dry ; 
to trust for some time to the moisture that exists in 
such earth, and in the atmosphere, for the supply re- 



164 APPLICATION OF PRINCIPLES. 

quired for germination ; and only to administer water 
when the signs of germination have become visible ; 
even then the supply should be extremely small. If 
this is attended to, carbonic acid is very slowly form- 
ed and liberated, the chemical quality of the contents 
of the seed is thus insensibly altered, each act of respi- 
ration may be said to invigorate it, and by degrees it 
will be brought to a condition favourable to the assi- 
milation of food in larger quantities. Mr. Knight 
used to say that these effects were produced in no way 
so .well as by enclosing seeds between two pieces of 
loamy turf, cat smooth, and applied to each other by 
the underground sides ; such a method is, however, 
scarcely applicable to any except seeds of consider- 
able size.* 

Other expedients have occasionally been had re- 
course to successfully. Where seeds are enclosed in 
a very hard dry shell, it is usually necessary to file it 
thin, so as to permit the embryo to burst through its 
integuments when it has begun to swell. Under natu- 
ral circumstances, indeed, no such operation is prac- 
tised : but it is to be remembered that such seeds will 
have fallen to the ground as soon as ripe, and before 
their shell acquired the bony hardness that we find 
after having become dry. 

Sometimes it has been found useful to immerse 

* The sowing of very small and delicate seeds in the open air 
should be deferred until the season is so far advanced, that all pro- 
bable danger from cold weather is past. Suspending a shingle or 
board over the place where they are sown, by laying it upon bricks 
placed edgewise, until the first leaves are perfectly formed, will be 
found a great advantage in sowing all delicate seeds. A. J. D. 



OF SEED-SOWING. 165 

seeds in tepid water until signs of germination mani- 
fest themselves, and then to transfer them to earth : 
but this process cannot be applied with advantage to 
seeds in an unhealthy state ; and it is only of use to 
healthy seeds, by accelerating the time of growth, a 
practice which may, in out-door crops, be sometimes 
■ desirable when applied to seeds which, like the Beet, 
the Carrot, or the Parsnep, will, in dry seasons, lie so 
long in the ground without germinating, that they 
become a prey to birds or other animals. 

Of late years, the singular practice has been intro- 
duced of boiling seeds, to promote germination. This 
was, I believe, first recommended by Mr. Bowie, who 
stated, in the Gardener's Magazine, vol. viii.p. 5, (1832,) 
that "he found the seeds of nearly all leguminous 
plants germinate more readily by having water heated 
to 200°, or even to the boiling point of Fahrenheit's 
scale, poured over them, leaving them to steep and 
the water to cool for twenty-four hours." Subse- 
quently, the practice has been adopted by other per- 
sons with perfect success ; and, some years ago, seed- 
lings of Acacia lophantha were exhibited before the 
Horticultural Society by the late Mr. Thomas Cary 
Palmer, which had sprung from seeds boiled for as 
much as five minutes. I am also acquainted with 
other cases, one of the more remarkable of which was 
the germination of the seeds of the Raspberry, picked 
from a jar of jam, and which must therefore have 
been exposed to the temperature of 230°, the boiling 
point of syrup. It is difficult to understand in what 
way so violent an action can be beneficial to any 



166 APPLICATION OF PRINCIPLES. 

thing possessing vitality ; the fact, however, is cer- 
tain. As such instances of success are confined to 
seeds with hard shells, it is possible that the heated 
fluid may act in part mechanically by cracking the 
shell, in part as a solvent of the matters enclosed in 
the seed, and in part as a stimulant. 

Mr. Lymburn, nurseryman at Kilmarnock, has 
lately called attention to the effect produced upon 
germinating seeds by alkaline substances. He states 
that experiments made by Mr. Charles Maltuen, and 
narrated in Brewster's Journal of Science, having 
shown that the negative or alkaline pole of a galvanic 
battery caused seeds to germinate in much less time 
than the positive or acid pole, he was induced to 
observe the effects on seeds of acetic, nitric, and sul- 
phuric acids, and also of water rendered alkaline by 
potash and ammonia. "In the alkaline, the seeds 
vegetated in thirty hours, and were well developed in 
forty ; while in the acetic and sulphuric they took 
seven days ; and, even after a month, they had not 
begun to grow in the acetic. " This experiment led 
to others upon lime ; "a very easily procured alkali, 
and which he inferred to be more efficient than any 
other from the well-known affinity of quick or newly 
slacked lime for carbonic acid. Lime, as taken from 
the quarry, consists of carbonate of lime, or lime 
united to carbonic acid ; but, in the act of burning, 
the carbonic acid is driven off; and hence the great 
affinity of newly slacked lime for carbonic acid. He 
depended, therefore, upon this affinity, to extract the 
carbon from the starch, assisted by moisture" (Gard, 



OF SEED-SOWING. 16? 

Mag., xiv. 74) ; and it is stated that the results were 
exceedingly striking. Old Spruce Fir seed, which 
would scarcely germinate at two years old, produced 
a fine healthy crop when three years old, having been 
first damped and then mixed with newly slacked 
lime ; and, under the same treatment, an average 
crop of healthy plants was obtained when the seed 
was four years old. Unfortunately, the manner in 
which the original experiments upon acids and alka- 
lies were conducted is not explained, (it is to be 
presumed that the water employed was only acidu- 
lated with the acids spoken of,) and I am not aware 
of the experiments having been repeated. — The last 
method of promoting germination, to which it is 
necessary to advert, is the mixing seeds with agents 
that have the power of liberating oxygen. It has been 
shown (14) that a seed cannot germinate until the car- 
bon with which it is loaded is to a considerable extent 
removed; the removal of this principle is effected by 
converting it into carbonic acid, for which purpose 
a large supply of oxygen is required. Under ordi- 
nary circumstances, the oxygen is furnished by the 
decomposition of water by the vital forces of the 
seed ; but, when those forces are languid, it has been 
proposed to supply oxygen by some other means. 
Humboldt employed a dilute solution of chlorine, 
which has a powerful tendency to decompose water 
and set oxj^gen at liberty, and, it is said, with great 
success. Oxalic acid has also been used for the same 
purpose. 

Mr. Otto, of Berlin, states that he employs oxalic 



168 APPLICATION OF PRINCIPLES. 

acid to make old seeds germinate. The seeds are put 
into a bottle rilled with oxalic acid, and remain there 
till the germination is observable, which generally 
takes place in from twenty-four to forty -eight hours ; 
when the seeds are taken out, and sown in the usual 
manner. Another way is to wet a woollen cloth 
with oxalic acid, on which the seeds are put, and it is 
then folded up and kept in a stove ; by this method 
small and hard seeds will germinate equally as well 
as in the bottle. Also very small seeds are sown in 
pots and placed in a hot-bed ; and oxalic acid, much 
diluted, is applied twice or thrice a day till they begin 
to grow. Particular care must be taken to remove 
the seeds out of the acid as soon as the least vegeta- 
tion is observable. Mr. Otto found that by this means 
seeds which were from twenty to forty years old 
grew, while the same sort, sown in the usual manner, 
did not grow at all (Gard. Mag., viii. 196) : and it is 
asserted by Dr. Hamilton (lb., x. 368, 453,) and 
others, that they have found decided advantages from 
the employment of this substance. Theoretically 
it would seem that the effects described ought to be 
produced, but general experience does not confirm 
them ; and it may be conceived that the rapid abstrac- 
tion of carbon, by the presence of an unnaturally 
large quantity of oxygen, may produce effects as 
injurious to the health of the seed as its too slow 
destruction in consequence of the languor of the vital 
principle. 

The length of time that some seeds will lie in the 
ground, under circumstances favourable to germi- 



OF SEED-SAVING. 169 

nation, without growing, is very remarkable, and 
inexplicable upon any known principle. If the Haw- 
thorn be sown immediately after the seeds are ripe, a 
part will appear as plants the next spring ; a larger 
number the second year ; and stragglers, sometimes 
in considerable numbers, even in the third and fourth 
seasons. Seeds of the genera Ribes, Berberis, and 
Pseonia, have a similar habit. M. Savi is related by 
De Candolle to have had, for more than ten years, a 
crop of Tobacco from one original sowing ; the young 
plants having been destroyed yearly, without being 
allowed to form their seed. This matter does not, 
perhaps, concern the theory of horticulture, for 
theory is incapable of explaining it ; but it is a fact 
that it is useful to know, because it may prevent still 
living seeds from being thrown away, under the idea 
that, as they did not grow the first year, they will 
never grow at all. 



CHAPTER VI. 

OF SEED-SAVING. 

The maturation of the seed being a vital action 
indispensable to the perpetuation of a species, is, in 
wild plants, guarded from interruption by so many 
wise precautions, that no artificial assistance is requir- 
ed in the process ; but in gardens, where plants are 
often enfeebled by domestication, or exposed to con- 



170 APPLICATION OF PRINCIPLES. 

ditions very different from those to which they are 
subject in their natural state, the seed often refuses to 
ripen, or even to commence the formation of an 
embryo. In such cases, the skill of gardeners must 
aid the workings of nature, and art must effect that 
which the failing powers of a plant are unable to bring 
about of themselves. 

Sterility is a common malady of cultivated plants ; 
the finer varieties of fruit, and all double and highly 
cultivated flowers, being more frequently barren than 
fertile. This arises from several different causes. 

The most common cause of sterility is an unnatural 
developement of some organ in the vicinity of the 
seed, which attracts to itself the organisable matter 
that would otherwise be applicable to the support of 
the seed. Of this the Pear, the Pine-apple, and the 
Plantain are illustrative instances. The more deli- 
cate varieties of Pear, such as the Gansel's Bergamot 
and the Chaumonteile, have rarely any seeds; of 
Pine-apple, none, except the Enville now and then, 
have seeds, and that variety, though a large one, is 
of little value for its delicacy, and probably ap- 
proaches nearly to the wild state of the plant ; of 
Plantains, few, except the wild and crabbed sorts, are 
seedful. The remedy for this appears to be, in with- 
holding from such plants all the sources from which 
their succulence can be encouraged. If, in conse- 
quence of any predisposition to form succulent tissue 
(on which the excellence of fruit much depends), the 
organisable matter of the plant be once diverted from 
feeding the seed to those parts in which the succu- 



OF SEED-SAVING. 171 

lence exists, it will continue, by the action of endos- 
mose, to be attracted thither more powerfully than to 
any other part, and the effect of this will be the 
starvation of the seed : but a scanty supply of food, 
an unhealthy condition of the plant itself, or with- 
holding the usual quantity of water, will all check 
the tendency to luxuriance, and therefore will favour 
the developement of the seed, whose feeble attracting 
force is, in that case, not so likely to be overcome by 
the accumulation of attracting power in the neigh- 
bouring parts. Thus we see the Pine-apples are 
more frequently seedful under the bad cultivation of 
the Continent, than in the highly kept and skilfully 
managed pineries of England. Abstraction of 
branches, in the neighbourhood of fruit, has also been 
occasionally found favourable to the formation of 
seed; evidently because the food that would have 
been conveyed into the branches, having no outlet, is 
forced into the fruit. 

Another cause of sterility is the deficiency of pollen 
(87) in the anthers of a given plant, as in vegetable 
mules (88), which usually partake of the spermatic 
debility so well known in similar cases in the animal 
kingdom. It has often been found that sterility of 
this kind is cured by the application, to the seedless 
plant, of the vigorous pollen of another less debilitated 
variety. 

In some plants, such as Pelargoniums, when culti- 
vated, the anthers shed their pollen before the stigma 
is ready to receive its influence, and thus sterility re- 
sults. All such cases are provided for, by employing 



172 APPLICATION OF PRINCIPLES. 

the pollen of another flower. (See Sweet in the Gar- 
dener's Magazine, vii. 206.) 

An unfavourable state of the atmosphere obstructs 
the action of pollen, and thus produces sterility. 
Pollen will not produce its impregnating tubes in too 
low a temperature, or when the air is charged with 
moisture ; neither, in the absence of wind or insects, 
have some plants the power of conveying the pollen 
to the stigma, their anthers having no special irrita- 
bility, and only opening for the discharge of the pollen, 
not ejecting it with force. If we watch the Hazel, or 
any of the Coniferous order, in which the enormous 
quantity of pollen employed to secure the impregna- 
tion of the seed renders it easy to see what happens, 
it will be found that no pollen is scattered in damp 
cold weather ; but, in a sunny, warm, dry morning, 
the atmosphere surrounding such plants is, in the im- 
pregnating season, filled with grains of pollen dis- 
charged by the anthers. In wet springs the crops of 
fruit fail, because the anthers are not sufficiently 
dried to shrivel and discharge their contents, which 
remain locked up in the anther cells till the power of 
impregnation is lost. In vineries and forcing-houses 
generally, into which no air is admitted to disturb the 
foliage, nor any artificial means employed for the 
same end, and when the season is too early for the 
presence of bees, flies, and other insects, the grapes 
will not set : and in the frames of melons and cucum- 
bers, from which insects are excluded, no seed is 
formed unless the pollen is conveyed by hand, from 
those flowers in which it is formed, to others in which 



OF SEED-SAVING. 173 

the young fruit alone is generated. In all cases of 
this kind, the remedy for sterility is obvious enough 
where plants exist in an artificial condition ; but, when 
they occur in the orchard or the flower-garden, in the 
open air, science suggests no assistance. 

It sometimes happens that particular parts of plants, 
distant from the fruit, are so constructed as to attract 
to themselves the food intended for the fruit, and thus 
to prevent the formation of seed. For exa^nple : — 
The early varieties of Potato do not readily produce 
seed, owing to the abstraction by their tubers of the 
nutritive matter required for the support of the seed. 
Mr. Knight found that by destroying the tubers in 
part, as they formed, seeds were readily procured from 
such varieties.* 

But perhaps the most frequent cause of sterility 
is the monstrous condition of the flowers of many cul- 
tivated plants. It has been fully explained (84) that 
the floral organs of plants are nothing more than 
leaves, so modified as to be capable of performing 
special acts, for particular purposes ; but they are 
not capable of performing those acts any longer than 
they retain their modified condition; and therefore 
the stamens cannot secrete pollen, when, by acciden- 
tal circumstances, they are changed into leaves, as 
happens in double flowers; then, there is nothing 

* Vice versa, the produce of the potatoes may be much increased 
by plucking off the blossoms, in which case the nutritive matter 
which would have been expended upon them and the berries, or 
fruit, serves to increase the size of the tubers, for which alone the 
plant is cultivated. This fact, so perfectly consistent with theory, 
has been completely confirmed by experiment. 



174 APPLICATION OF PRINCIPLES. 

to fertilise the stigma, and, of course, no seed is pro- 
duced. Or the carpels themselves may be converted 
into leaves, and have lost their seed-bearing property. 
Double flowers in the latter case cannot possibly bear 
seed ; but in the condition first mentioned they may, 
and often do. To bring this about, the cultivator 
plants in the vicinity of his sterile flowers others of 
the same species, in which a part at least of the 
stamens are perfect, and they furnish a sufficiency of 
pollen for the impregnation of the other flowers in 
which there are no stamens. 

In some cases, principally in those of Composite 
flowers, the seed is formed and advanced towards 
perfection, and then decays ; this is owing to the 
flower heads of such plants being composed, in a great 
measure, of soft scales, absorbent and retentive of 
moisture, to which, in their own country, they are 
not exposed in the fruiting season, but by which they 
are affected under the hands of the cultivator. When 
the heads of such flowers are soaked with moisture, 
which they cannot get rid of, the scales rot, and decay 
spreads to all the other parts, and thus the production 
of seed is prevented. The Chinese Chrysanthemum 
is a familiar instance of this. Such plants seed rea- 
dily if the flower heads are kept warm and dry ; and 
it is thus that the sterile Chrysanthemum has been 
made seedful; that is to say, by growing it in a 
dry warm winter border, protected from showers by 
a roof of glass, or by using some such means of guard- 
ing it ; or by rearing it in a warm dry climate. 

When seeds are freely produced, it is not altoge- 



OP SEED-SAVING, 175 

tlier a subject of indifference in what way they are 
saved, if it is desired that their progeny should be the 
most perfect that can be obtained. Weak seeds 
produce weak plants, and therefore recourse should 
be had, in all delicate cases, to artificial means for 
giving vigour to the seed. In general, the cultivator 
trusts to his eye for separating the plumpest and most 
completely formed seeds; or to floating them in 
water, selecting only the heavy grains that sink, and 
rejecting all those which are buoyant enough to float. 
But the energy of the vital principle in a seed may be, 
undoubtedly, increased by abstracting neighbouring 
fruits, by improving the general health of the parent 
plant, by a full exposure of it to light, and by pro- 
longing the period of maturation as much as is con- 
sistent with the health of the fruit. It is a constant 
rule that seedlings take after their parents, an unheal- 
thy mother producing a diseased offspring, and a 
vigorous parent yielding a healthy progeny in all 
their minute gradations and modifications; and this is 
so true, that, as florists very well know, semi-double 
Ranunculi, Anemones, and similar flowers, will rarely 
yield double varieties, while the seeds of the latter as 
unfrequently give birth to semi-double degenerations. 
Independently of these things, it is indispensable that 
the seed of a plant, when saved, should be perfectly 
ripe, if it is intended to be laid by for future sowing. 
The effect of ripening is to load the seed with carbon 
in the form of starch, or some such substance (102), 
and to deprive it of water, conditions necessary for 
its preservation ; but, if a seed is gathered before 



176 APPLICATION OF PKINCIPLES. 

being ripe, these conditions are not secured ; and, in 
proportion to the deficiency of carbon and superabun- 
dance of water, is the seed liable to perish. 

The complete maturation of the seed is, however, a 
disadvantage, when it has to be sown immediately 
after being gathered j for the embryo is formed, and 
capable of germinating, long before the period of 
greatest maturity. There are two periods in the 
latter part of the organisation of a seed which, 
although separated by no limits, require to be distin- 
guished. The first is that when the embryo is com- 
pleted ; and the second is when nature has, in ad- 
dition, furnished it with the means of maintaining 
its vitality for a long j)eriod. It is just as capable of 
growing at the expiration of the first period as of the 
second ; it will do so iminediatety if committed to the 
ground, and we see it actually happening to Peas, 
Beans, Corn, and other field crops, in wet summers ; 
but, at the end of the second period, it cannot germi- 
nate till it has relieved itself of all the carbon which, 
during that period, was deposited in its tissue. 

If seeds are to be preserved for a length of time, a 
state of complete dryness is so necessary to them that 
it has been recommended to increase it by artificial 
means : not, however, by the application of heat, or 
by any process like that of kiln-drying, for that would 
destroy their vitality ; but by some of those chemical 
processes which dry the atmosphere without raising 
its temperature. It occurred to Mr. Livingstone, that 
air made dry by means of sulphuric acid might be 
advantageously employed for this purpose, and he 



OF SEED-PACKING. 177 

says that the success of his experiments was com- 
plete. He placed the seeds to be dried in the pans 
of Leslie's ice machine, and carefully replaced the 
receiver without exhausting the air; small seeds 
were sufficiently dried in one or two days, and the 
largest seeds in less than a week. (Eort. Trans., iii. 
184.) 

Other contrivances might easily be adopted. Muri- 
ate of lime, for instance, which has the property of 
absorbing the moisture of the atmosphere, might, per- 
haps, be employed with advantage in drying the air 
in which seeds are placed after being gathered. 

The reason why it is so important that seeds which 
have to be long kept should be thoroughly dried, is, 
partly because seeds have the power of decomposing 
water, which causes the commencement of germina- 
tion (14), and, if this happens while they are cut off 
from the other means of existence, the process of 
growth must be stopped, and their death will follow 
and, in part, from the tendency of vegetable matter in 
contact with water to putrefy, if the actions of life are 
not in play. 



CHAPTER VII. 

OF SEED-PACKING. 

It seldom happens that seeds are sown as soon as 
they are ripe : it is sometimes desirable that they 

S* 



178 APPLICATION OF PRINCIPLES. 

should be preserved for long periods of time : the 
power of conveying them for great distances, through 
various climates, is one of those upon which man most 
depends for the improvement of the horticultural re- 
sources of all countries; and for this purpose large 
sums are annually expended, both by governments 
and individuals. It is, therefore, an object of the first 
importance to ascertain, what is not well understood, 
as it would seem, namely, the causes by which the 
destruction of the germinating power of seeds is 
effected; for it is only by doing this that their pre- 
servation can be secured. 

Seeds are probably possessed of different powers of 
life, some preserving their vital principle through 
centuries of time, while others have but an epheme- 
ral existence under any circumstances. The reasons 
for this difference are unknown to us, and apparently 
depend upon a first cause, over which we have, 
therefore, no control ; bat the fact of great longevity 
in some seeds is certain, and there seems no reason 
why the conditions which enable them to preserve 
their germinating power for long periods of time 
should not be discovered and imitated. 

Without admitting such doubtful cases as those of 
seeds preserved in mummies having germinated, there 
are many instances of seminal longevity about which 
there can be no doubt. Books contain an abundance 
of instances of plants having suddenly sprung up from 
the soil obtained from deep excavations, where the 
seeds must be supposed to have been buried for ages. 
Professor Henslow says that in the fens of Cambridge- 



OF SEEI>PAC&I^& 179 

shire, after the surface has been drained and the soil 
ploughed, large crops of white and. black mustard 
invariably appear. Miller mentions a case of Plan- 
tago Psjdliuni having sprung from the soil of an 
ancient ditch which was emptied at Chelsea, although 
the plant had never been seen there iia the memory 
of man, De Candolle says that M. Grerardin succeed- 
ed in raising Kidneybeans from seed at least & hun- 
dred years old, taken out of the herbarium of Tourne- 
fort ; and I have myself raised Easpberry plants from 
seeds found in an ancient coffin, in a barrow in Dor- 
setshire, which seeds, from the coins and other relics 
met with near them, may be estimated to have bee& 
sixteen or seventeen hundred years old. 

In these cases, the only circumstances that we can 
conceive to have operated must have been such a de- 
gree of dryness as prevented the decomposition of the 
seed on the one hand, and the excitement of its germi- 
nating powers on the other, a moderately low tempe- 
rature, and m some of them the exclusion of air ; for 
moisture, heat, and communication with the air, are 
necessary to enable seeds to grow (14). The tendency 
of moisture exposed to the air, and in contact with 
inert vegetable matter, such as a torpid seed, is by de- 
grees to produce decay, which rapidly spreads to the 
neighbouring parts. But, if the vitality of a seed is 
excited by a fitting temperature, the moisture with 
which it is in contact is then decomposed, the oxygen 
so obtained combines with the carbon of the seed, and 
forms carbonic acid, which flies off, and by degrees re- 
duces the amount of carbon lodged in the tissue of the 



180 APPLICATION OF PRINCIPLES, 

seed to that which is best suited for the growth of the 
embryo (103) ; then, if the embryo is so situated that it 
cannot obtain from the surrounding medium food upon 
which to subsist, its germination stops, and, being de- 
prived of its carbon, the safeguard of its vitality is re- 
moved, and it perishes. If, however, the amount of 
moisture in contact with a seed is very small, as in the 
dry earth at the bottom of a tumulus for instance, the 
temperature at the same time low, and the access of at- 
mospheric air cut off, neither putrefaction nor germi- 
nation is likely to occur. If seeds are exposed to a 
high temperature in dryness, they will not perish un- 
less the temperature rises beyond anything likely to 
occur under natural circumstances. Edwards and 
Colin found that even wheat, barley, and rye, inhabit- 
ants of temperate countries, would bear when'dry 104° 
for a long time without injury, although they died in 
three days in water at 95° ; and a much higher pro- 
, longed temperature may be expected to produce no 
ill effect upon seeds inhabiting hotter countries. 
There is no apparent reason why the exposure of dry 
seeds to the air should destroy vitality, unless the ex- 
posure is very much prolonged ; nor have we any 
evidence to show that it ddes, so long as they remain 
dry. The way in which the atmosphere would act 
injuriously upon dormant seeds is, by its oxygen ab- 
stracting their carbon ; and it was formerly supposed 
that the carbonic acid extricated by germinating seeds 
# was formed in this way. But the very valuable ob- 
servations and experiments of Messrs. Edwards and 
Colin (see Comptes rendus de VAcademie des Sciences, 



OF SEED-PACKING- 181 * 

vii. 922,) show that carbonic acid is formed by the as- * 
sistance of the oxygen obtained by the decomposition 
of water. 4 

If we apply these considerations to the plans usually 
employed for preserving artificially the # vitality of • , 
seeds, we shall find them offer a ready explanation of 
the success that attends some methods of packing, ancl 
the constant failure of others. 

The great object of those who have devised means 
of packing seeds for distant journeys has, in general, 
been to exclude the air, and* all other, considerations 
have been subordinate to this. Enelosurein bottles' •.. 
hermetically sealed, in papers thickly coated with 
wax, in tin boxes, and similar contrivances, have been 
resorted to with this object in view: but no advan- 
tage can be derived from excluding the air, and the 
disadvantage is very great ; for the effect of exclud- 
ing the air is to include whatever free moisture seeds 
may con tarn or be surrounded by ;.Vthis moisture is . 
sufficient, in high temperatures,, either to deprive the-" 
seed of its carbon of preservation, or to induce 'decay '^ 
of the tissue, especially of the seed-coats, whisji have. m 
no vitality themselves, and in either case the embryo 
perishes. 

Packing in charcoal has been recommended, it is 
difficult to say why; and experience shows what 
might have been anticipated, that it produces no Othpi*. . 
effect than' packing • in. earth "or other, dry non.-con- . 
ducting -material. >. : ' -•■■'" V--\ ['■. : \- . * ' 

. Clayed sugar has been employe^ ^ndj' as' it is sai.4, •« 
occasionally with advantage ; but I have seen no in- 



182 APPLICATION OF PRINCIPLES. 

stance of success, and, on the contrary, its tendency 
to absorb moisture from the air till it becomes capable 
of fermenting, is in itself an objection to the employ- 
ment of this substance. 

The most common method of packing is to enclose 
seeds in paper, to surround parcels of such papers 
with envelopes of the same material, and to enclose 
the whole in a deal box. It is in this manner that 
seedsmen usually despatch their orders to India, and 
other distant parts of the world. The evils of this 
method have been pointed out by Dr. Falconer, in 
the Proceedings of the Horticultural Society, vol. i. p. 
49. a On one occasion," he says, " I received from 
England a large assortment of garden vegetable seeds, 
from a London seedsman. They were packed in the 
thick dark brown paper which is generally used by 
grocers and seedsmen, and which, for the facility of 
folding, is usually in a somewhat damp state. The 
packages were nailed up in a large wooden box, with 
numerous folds of this paper, and the box was then 
hermetically sealed in a tin case ; it then found its way 
into the ship's hold. The damp paper, which in the 
temperature of England, say at 50°, would have mat- 
tered little, became an important agent when the ship 
got into the tropics ; at about 80° the damp became a 
hot vapour, and, when the seeds reached me, I found 
them all in a semi-pulpy and mildewed state." 

Upon the whole, the only mode which is calculated 
to meet all the circumstances to which seeds are ex- 
posed during *a voyage is to dry them as thoroughly 
as possible, enclose them in coarse paper, and to pack 



OF PROPAGATION BY EYES AND KNATJRS. 183 

the papers themselves very loosely in coarse canvass 
bags, not enclosed in boxes, but freely exposed to the 
air ; and to insure their transmission in some dry 
well-ventilated place. Thus, if the seeds are origi- 
nally dried incompletely, they will become further 
dried on their passage ; if the seed paper is damp, as 
it almost always is, the moisture will fly off through 
the sides of the bags, and will not stagnate around the 
seeds. It is true that, under such circumstances, the 
seeds will be exposed to the fluctuations of tempera- 
ture, and to the influence of the atmosphere ; but nei- 
ther the one nor the other of these is likely to be pro- 
ductive of injury to the germinating principle. The 
excellence of this method I can attest from my own 
observation. Large quantities of seeds have been 
annually transmitted from India for many years, 
doubtless gathered with care, it is to be presumed 
prepared with every attention to the preservation of 
the vital principle, and certainly packed with all those 
precautions which have been erroneously supposed 
to be advantageous ; the hopelessness of raising plants 
from such seeds has at length become so apparent, 
that many persons have altogether abandoned the 
attempt, and will not take the trouble to sow them 
when they arrive. But the seeds sent from India by 
Dr. Falconer, packed in the manner last described, ex- 
posed to all the accidents which those first mentioned 
can have encountered, have germinated so well, that 
we can scarcely say that the failure has been greater 
than if they had been collected in the south of Europe. 
I have no doubt that the general badness of the 



184 



APPLICATION OF PRINCIPLES. 



seeds from Brazil, from the Indian Archipelago, and 
from other intertropical countries, is .almost always 
to be ascribed to the seeds having been originally in- 
sufficiently dried, and then enclosed in tightly packed 
boxes, whence the superfluous moisture had no means 
of escape. 

For seeds containing oily matter, which are pecu- 
liarly liable to destruction (by their oil becoming 
rancid ?), ramming in dry earth has been found advan- 
tageous ; as in the case of the Mango. 



CHAPTER VIII. 

OF PROPAGATION BY EYES AND KNAUR& 

The power of propagating plants by any other 
means than that of seeds depends entirely upon the 
presence of leaf-buds {fig. 16), or. as they are technical- 




OF PROPAGATION BY EYES AND KXAURS. 185 

ly called, "eyes" (52), which are in reality rudimentary 
branches in close connexion with the stem. All stems 
are furnished with such buds, which, although held 
together by a common system, have a power of inde- 
pendent existence under fitting circumstances ; and, 
when called into growth, uniformly produce new 
parts, of exactly the same nature, with respect to each 
other, as that from which they originally sprang. 

Under ordinary circumstances, an eye remains fix- 
ed upon the stem that generates it. There it grows, 
sending woody matter downwards over the alburnum, 
and a new branch upwards, clothed with leaves, and 
perhaps flowers : but it occasionally happens that 
eyes separate spontaneously from their mother stem, 
and when they fall upon the ground they emit roots 
and become new plants (p. 29. fig. 3). This happens 
in several kinds of Lily, and in other genera. 

Man has taken advantage of this property, and has 
discovered that the eyes of many plants, if separated 
artificially from the stem and placed in earth, will, 
under favourable circumstances, produce new plants, 
just as such eyes would have done if they had spon- 
taneously disarticulated ; hence the system of propa- 
gation by eyes, an operation employed only to a 
limited extent in actual practice, but which in theory 
seems applicable to all plants whatever. The only 
species very generally so increased are the Potato and 
the Tine. Of the latter, the eye, with a small portion 
of the stem adhering to it, is commonly taken as the 
means of obtaining young plants ; being placed in 
earth, with a bottom heat of 75° or 80°, and kept in 



186 APPLICATION OF PRINCIPLES. 

a damp atmosphere, it speedily shoots upwards into 
a branch, and at the same time establishes itself in 
the soil by the developement of the requisite quantity 
of roots. In order to insure success in this operation 
upon the Vine, it is only necessary that the eye 
should be dormant, and that a small piece of well- 
ripened wood should, as has been already stated, be 
separated with it ; it will then grow in much the same 
way and under the same circumstances as a seed. 
There is no doubt that many plants could be thus 
multiplied just as easily as the Vine, but it is equally 
certain that a far larger number cannot be so increas- 
ed. The reason of this is, probably, that such eyes 
are not sufficiently excitable, and that consequently 
they decay before their vital energies are roused; 
and, in addition, that the}^ do not contain within 
themselves a sufficient quantity of organisable matter 
upon which to exist until new roots are formed, capa- 
ble of feeding the nascent branch. 

Mr. Knight's explanation of this, although in part 
applicable to cuttings onh T , yet seems to deserve 
being introduced in this place. " Every leaf-bud 
is well known to be capable of extending itself into a 
branch, and of becoming the stem of a future tree ; 
but it does not contain, nor is it at all able to prepare 
and assimilate, the organisable matter required for its 
extension and development. This must be derived 
from a different source, the alburnous substance of 
the tree, which appears the reservoir, in all this tribe 
of plants, in which such matter is deposited. I found 
a very few grains of alburnum to be sufficient to sup- 



OF PROPAGATION BY EYES AND KNAURS. 187 

port a bud of the Vine, and to occasion the formation 
of minute leaves and roots : but the early growth of 
such plants was extremely slender and feeble, as if 
they had sprung from small seeds ; and the buds of 
the same plant, wholly detached from the alburnum, 
were incapable of retaining life. The quantity of 
alburnum being increased, the growth of the buds 
increased in the same proportion ; and when cuttings 
of a foot long, and composed chiefly of two-years old 
wood, were employed, the first growth of the bads 
was nearly as strong as it would have been, if the 
cuttings had not been detached from the tree. The 
quantity of alburnum in every young and thriving 
tree, exclusive of the Palm tribe, is proportionate to 
the number of its buds ; and if the number of these 
were, in any instance, ascertained and compared with 
the quantity of alburnous matter in the branches and 
stem and roots, it would be found that nature has 
always formed a reservoir sufficiently extensive to 
supply every bud. But those of a cutting, under 
the most favourable circumstances, must derive their 
nutriment from a more limited and precarious source ; 
and it is therefore expedient that the gardener should, 
in the first instance, make the most ample provision 
conveniently within his power for their maintenance, 
and that he should subsequently attend very closely 
to the economical expenditure of such provision." 
(Horticultural Transactions, ii. 115.) 

In the Potato the requisite provision of organ i sa- 
ble matter is always secured, in consequence of the 
great difficulty of separating an eye of that plant. 



188 APPLICATION OF PRINCIPLES. 

without fragments of the amylaceous tuber adhering 
to it. 

The provision of alimentary matter may, however, 
be, in some cases, disadvantageous, by promoting too 
great a development of stems and leaves, of which the 
Potato itself is an instance. Theoretically, the more 
nutritive matter there is for the eyes, the greater crop 
there will be, cceteris paribus, and so there probably is 
of leaves and stems ; and it would seem that whole 
potatoes should be more advantageous to plant than 
sets. But I have proved, by a series of numerous 
experiments, that the weight of potatoes per acre 
is greater, under equal circumstances, from sets than 
from whole tubers, by upwards of from seven cwt.' to 
three tons per acre ; and considerably more, on com- 
parison of the clear produce, after deducting the 
weight of sets employed in both cases. (Rort. Trans. 
n. s., i. 445, and ii. 156.) In these instances, I sup- 
posed the rankness of the vegetation from the whole 
tubers to be the cause of the diminished crop, for the 
stems were unable to support themselves, and were 
blown about, laid, and broken by the wind. 

"While, however, in such plants as the Potato, all 
the eyes were equally capable of forming new tubers, 
it is found by experience that they do so with differ- 
ent degrees of rapidity, according to the age of that 
part of the stem or tuber which furnishes them. It 
is stated by a writer in the Gardener's Magazine (vol. 
i. p. 406), that it is well known in Lancashire to some 
cultivators of the Potato, " that different eyes germi- 
nate, and give their produce, or become ripe, at times 




OF PROPAGATION BY EYES AND KNAURS. 189 

varying very materially, say several weeks, from 
each other ; some being ripe or fit for use as early as 
the middle of May, and others not till 
June or July. This will be understood 
by reference to the accompanying 
sketch. The sets nearest the extremity 
of the Potato {fig. 17, a) are soonest ripe, 
and in Lancashire, are planted in warm 
places in March or the beginning of 
April, and are ready for the market 
about the 12th or 15th of May. The 
produce of the next sets (b) is ready in about a fort- 
night after, and that from the root end (c and d) still 
later. These roots and sets (from b to d) are usually 
put together, and the extremity of the root end is 
thrown aside for the pigs." This fact, if correctly 
stated, shows, not that the youngest eyes, or those 
nearest the point of the Potato, are the ripest, which 
is impossible, but that they are more excitable, and 
consequently grow more rapidly than those at the 
middle or base. 

Besides the cases of propagation by eyes now men- 
tioned, there is another of which a notice is given by 
Signor Manetti (Gardener's Magazine, vii. 663), as 
practised in Italy upon the Olive. It appears that, 
from old Olive trees, certain knots or excrescences, 
called uovoli, are cut out of the bark, of which a por- 
tion is left adhering to them, and being planted, grow 
into young Olive trees. Of these I have no further 
account ; but it is evident that the uovoli are no other 
than our knaurs, already spoken of (53) under the 



190 APPLICATION OF PKINCIPLES. 

name of embryo buds ; concretions found in the bark 
of many, and probably of all, trees, and supposed to 
have been adventitious buds developed in the bark, 
and, by the pressure of the surrounding parts, forced 
into those tortuous woody masses in the shape of 
which we find them. They, in general, present an 
oblong or conical form, are sometimes collected into 
clusters, and usually exhibit little or no appearance 
of a tendency to further growth. It is, however, 
not uncommon to find them lengthening into branches 
as is shown in a Poplar, for which I am indebted to 
Sir Oswald Mosley ; and although they have never 
yet been used for the purposes of propagation, except 
in the case of the Olive, there seems to be no reason 
why they should not be so employed, if any neces- 
sity were to arise for them. The real amount of 
their powers of growth is unknown, and would be a 
good subject of investigation. 



CHAPTER IX. 

OF PROPAGATION BY LEAVES. 

In the beginning of the last century, Richard 
Bradley, a Fellow of the Royal Society, published a 
translation from the Dutch of Agricola, of a book 
upon the propagation of plants by leaves ; in which 
it was asserted that, by the aid of a mastic invented 
by the author, the leaves of any plant, dipped at the 



OF PROPAGATION BY LEAVES. 191 

stalk end into this preparation, would immediately 
strike root ; and the book was adorned with copper- 
plates exhibiting both the process and its result, 
in the form of fields stuck full of Orange leaves grow- 
ing into trees. 

Although this work was very absurd, yet it proba- 
bly originated in the discovery that the leaves of 
some plants will grow under special circumstances ; 
a fact often supposed to be much more rare than 
it really is. In Professor Morren's French Transla- 
tion of my Outlines of the First Principles of Horticul- 
ture, Kochea falcata* is named as producing adventi- 
tious buds (53) from the upper side of its leaves ; and 
the Orange, the Aucuba, and the Fig, as other 
instances of leaves which will multiply their species 
(p. 152) ; the power of Bryophyllum to do the same 
thing is familiar to every one. Hedwig found the 
leaves of the Crown Imperial, put into a plant-press, 
produce bulbs from their surface. There is a well- 
known case of the same effect having been observed 
in Ornithogalum thyrsoideum. M. Auguste de St. 
Hilaire mentions an instance of leaf-buds generated 
by fragments of the leaves of " Theophrasta," which 
had been buried by M. Neumann, chief gardener 
at the Garden of Plants at Paris, and of young Dro- 
seras furnished by the leaves of Drosera intermedia. 
Mr. Henry Cassini is said to have seen young plants 
produced by the leaves of Cardamine prate nsis ; Eng- 
lish botanists know that offsets spring from the mar- 
gins of the leaves of Malaxis paludosa; in our stoves 

* See, also, De Candalle's Physiologie Y6g6tale, ii. 6*72. 



192 APPLICATION OF PRINCIPLES. 

we see Ferns of many kinds, especially Woodwardia 
radicans, propagating themselves by offsets from the 
leaves ; Mr. Turpin tells us that floating fragments 
of Watercress leaves, cut up by a species of Phryga- 
nea for its nest, " produce presently from their base, 
and below the common petiole, at first two or three 
colourless roots, then in their centre a small conical 
bud, green, in which are found, or rather from which 
successively arise, all the aerial parts of a new Water- 
cress plant, while the roots multiply and lengthen." 
(Comjites rendus, 1839, sem. 2, 438.) Mr. Flourens 
also mentions a case of Purslane, whose leaves, 
divided into three, produced as many new plants, 
each having a root, stem, and leaves. In the Tram- 
actions of the Horticultural Society, is an account of 
a Zamia each of whose scales produced a new plant, 
when the central part of the stem was decayed. 
Finally, the following case is named in the same 
work (vol. v. p. 442,) by Mr. Knight : — 

" In an early part of the summer, some leaves of 
Mint (Mentha piperita), without any portion of the 
substance of the stems upon which they had grown, 
were planted in small pots, and subjected to artificial 
heat, under glass. They emitted roots, and lived 
more than twelve months, having assumed nearly the 
character of the leaves of evergreen trees ; and upon 
the mould being turned out of the pots, it was found 
to be everywhere surrounded by just such an inter- 
woven mass of roots as would have been emitted by 
perfect plants of the same species. These roots pre- 
sented the usual character of those organ?, and con- 



OF PROPAGATION BY LEAVES. 



193 



sisted of medulla, alburnum, bark, and epidermis; 
and as the leaf itself, during the growth of these, in- 
creased greatly in weight, the evidence that it gene- 
rated the true sap which was expended in their for- 
mation appears perfectly conclusive." 

In our gardens, we know of many other cases of 
the same kind. Hoya is a common instance, and three 
others are here figured {fig. 18) ; viz., Gesnera (a), 




194 APPLICATION OF PRINCIPLES. 

Clianthus puniceus (6), Gloxinia speciosa (c). In these, 
and all such cases, the first thing that happens is an 
excessive development of the cellular tissue, which 
forms a large convex "callus" at the base; from 
which, after a time, roots proceed ; and by which 
eventually a leaf-bud, the commencement of a new 
stem, is generated. 

It is not surprising that leaves should possess this 
quality, when we remember that every leaf does the 
same thing naturally while attached to the plant that 
bears it ; that is to say, forms at its base a bud which 
is constantly axillary to itself. Leaves, however, 
have not been often employed as the means of pro- 
pagating a species; and it is probable that most 
leaves, when separated from their parent, are incapa- 
ble of doing so, for reasons which we are not as yet 
able to explain. The most common case of their em- 
ployment is in the form of the scales of a bulb, which 
will, with some certainty, produce new plants under 
favourable circumstances. Those circumstances are, 
a strong bottom heat, moderate moisture, and a rich 
stimulating soil. 

When plants are produced by leaves under ordinary 
circumstances, the conditions most favourable to their 
doing so are of the same nature. A moderate amount 
of moisture prevents their dying from perspiration or 
perishing from decay ; a good bottom heat stimulates 
their vital forces, and causes them to exercise what- 
ever power they possess ; and, in addition, they are 
covered by a slightly shaded bell glass, which main- 
tains around them an atmosphere of uniform humi- 



OF PROPAGATION BY CUTTINGS. 195 

dity, and, at the same time, cuts off the approach of 
those direct solar rays, which, acting as a stimulus to 
perspiration, would have a tendency to exhaust the 
leaves of their fluid before they could organize, at 
their base, the new matter from which the leaf-bud is 
evidently produced. 



CHAPTER X. 
OF PROPAGATION BY CUTTING& 

This, which is the most common of all modes of 
artificial propagation except grafting, depends upon 
essentially the same principle as propagation by eyes; 
that is to say, the pieces of a plant called cuttings 
possess a power of growth in consequence of their 
bearing leaf-buds or eyes upon their surface. In 
striking by eyes, we have the great difficulty to en- 
counter of keeping the eye active till it has organised 
roots with which to feed itself; the earth furnishes 
such a supply unwillingly or unsuitably, nature in- 
tending that the bud should, in the first instance, be 
supported by the soluble nutriment ready prepared 
and lodged in its immediate vicinity, in the pith or 
some other part of the stem. For this reason, cut- 
tings, which consist of eyes and the part containing 
their proper aliment, usually strike root more freely 
than eyes by themselves. 

This being so, it is plain that a cutting is only capa- 
ble of multiplying a plant when it bears buds upon its 



196 



APPLICATION OF PRINCIPLES. 



surface ; and as the stem is the only part upon which 
buds certainly exist, so the stem is the only part from 
which cuttings should be prepared. And again, as the 
internode, or that space of the stem which intervenes 
between leaf and leaf, has no buds, their station being 
confined to the axil of 
the leaves, a cutting pre- 
pared from an internode 
only is as improper as 
one from the root. It * 
is no doubt true, that 
we constantly propagate 
plants from pieces of 
what are called roots, as 
in the Potato, or the Scir- 
pus tuberosus {Jig. 19) ; 
but such roots are, in 
reality, the kind of stem called a tuber (51) ; and, in 
like manner, other cases of similar propagation are 
also successful, because the part called a root is, in 
reality, an underground stem covered with the rudi- 
ments of leaves, to each of which an eye belongs. 
The Eose, the Lilac, and many other plants, have 
subterranean stems, cuttings of which will there- 
fore answer the purpose of propagation. It will 
also occasionally happen, that, owing to unknown 
causes, morsels of the true root will generate what 
are called adventitious buds ; and hence we do 
occasionally see the root employed for propagation, 
as in Cydonia japonica ;* but these are rare and ex- 

* Also the Paper Mulberry, the Paulownia, Ac A J. D. 




OF PROPAGATION BY CUTTINGS. 197 

ceptional cases, and by no means affect the general 
rule. Mr. Knight attempted to account for this, by 
supposing that the powers which roots of various 
forms, and cuttings, and other detached parts of 
plants, possess of emitting foliage, " are wholly, and 
in all cases, dependent upon the presence of true sap 
previously deposited within them." (Hort. Trans., v. 
242.) But this is a very obscure expression, and 
does not seem to throw any light upon the subject. 

When the vine grows in a very warm damp stove, 
its stem emits roots into the air ; the same thing hap- 
pens to the Maize on the lower part of its stem ; and 
in these and all such cases, the roots are found to be 
emitted from buds. Hence it has been inferred that 
the roots of a plant are as much productions of buds 
as branches are, and that the stem is nothing more than 
a collection of such roots held together under the form 
of wood and bark. The present is not the place for 
a renewal of this discussion, for the arguments in 
favor of and opposed to which, the reader is referred 
to my Introduction to Botany, 3d edit. p. 309, &c. It 
is sufficient here to remark that the question turns 
upon whether the buds and leaves actually them- 
selves produce roots, or merely furnish the organis- 
able matter out of which roots are formed ; and that, 
therefore, for the purpose of horticulture, either the 
one or the other is equally capable of explaining the 
facts connected with cuttings.* 

* The following curious fact, recorded by Mr. Livingstone, which 
seems to have escaped observation, deserves to be mentioned here :— 
" The Pterocarpus Marsupium, one of the most beautiful of the large 



198 APPLICATION OF PRINCIPLES. 

As far as physiology can explain the operation of 
propagation by cuttings, it appears that roots are 
formed by the action of leaves ; that branches are de- 
veloped from the buds ; and that the buds are main- 
tained by the suitable aliment stored up in the stem. 
Every thing beyond this seems to be connected with 
specific constitutional powers, of which science can 
give no explanation. 

In considering what conditions are most favourable 
to the maintenance of a cutting in the state required, 
in order to enable it to become a young plant, it will 
be most convenient, in the first place, to examine the 
rationale of some one method which is known to be 
successful. For this purpose, the following detail, by 

trees of the East Indies, and which grows in the greatest perfection 
about Malacca, affording, by its elegant wide-expanding boughs, 
and thick-spreading pinnated leaves, a shade equally delightful 
with the far-famed Tamarind tree, is readily propagated by cuttings 
of all sizes, if planted even after the pieces have been cut for many 
months, notwithstanding they appear quite dry, and fit only for the 
fire. I have witnessed some of three, four, five, six, and seven 
inches in diameter, and ten or twelve feet long, come to be fine trees 
in a few years. While watching the transformation of the log into 
the tree, I have been able to trace the progress of the radicles from 
the buds, which began to shoot from the upper part of the stump a 
few days after it had been placed in the ground, and marked their 
progress till they reached the earth. By elevating the bark, minute 
fibres are seen to descend contemporaneously as the bud shoots into 
a branch. In a few weeks these are seen to interlace each other. 
In less than two years the living fibrous system is complete ; in five 
years no vestige of its log origin can be perceived ; its diameter 
and height are doubled, and the tree is in all respects as elegant 
and beautiful as if it had been produced from seed." (Hort. Trans., 
iv. 226.) 



OF PKOPAGATION BY CUTTINGS. 199 

Mr. Knight, of his mode of striking the Mulberry, is 
selected : — 

" A considerable number of cuttings were taken 
from the most vigorous bearing branches of a Mul- 
berry tree, in the middle of November, 1812, and 
were immediately reduced to the length adapted to 
small pots, in which I proposed them ultimately to be 
planted, and which were between four and five inches 
deep. Each cutting was composed of about two parts 
of two-years-old wood, that is, wood of the preceding 
year, and about one third of yearling wood, the pro- 
duce of the preceding summer ; and the bottom of 
each was cut so much aslope, that its surface might 
be nearly parallel with that of the bottom of the pot 
in which it was to be placed. 

" The cuttings were then inserted in the common 
ground, under a south wall, and so deeply immersed 
in it, that one bud only remained visible above its 
surface ; and in this situation they remained till April. 
At this period the buds were much swollen, and the 
upper ends of the cuttings appeared similar to those 
of branches which had been shortened in the preced- 
ing autumn, and become capable of transmitting any 
portion of the ascending fluid. The bark at the lower 
ends had also begun to emit those processes which 
usually precede the production of roots. The cuttings 
were now removed to the pots to which they had 
been previously fitted, and placed in a moderate hot- 
bed ; and a single bud only of each cutting remained 
visible above the mould, and that being partially co- 
vered ; and in this situation they vegetated with so 



200 APPLICATION OF PRINCIPLES 

much vigour, and emitted roots so abundantly, that I 
do not think one cutting in a hundred would fail, 
with proper attention. Some of the pots were placed 
round the edges of a melon bed, which affords a very 
eligible situation where a few plants only are want- 
ed." (Horticultural Transactions, ii. 117.) In this 
case success appears to have depended upon the fol- 
lowing circumstances: — 

1. The cuttings were prepared in November, at the 
end of the season of growth, when all the organisable 
matter required for the cutting was formed, and 
locked up in the proper places in its interior. It was 
not necessary, therefore, to take any means of insur- 
ing a further supply of aliment. But had it been 
otherwise, that is to say, if the cuttings had been pre- 
pared in the summer, in the midst of their growth, it 
would have been indispensable to allow a leaf or two 
to remain attached to the upper end of the cutting, 
to assist in the formation of alimentary matter. 

2. Although but one eye was allowed to grow, yet 
the cuttings themselves were four or five inches long, 
and they consisted, to the extent of two thirds, of 
two-years-old wood. By this means the quantity 
of food for the nascent branch was intended to be so 
great as to insure it against suffering from an inade- 
quate supply, until it had formed roots. The im- 
portance of this has already been shown by Mr. 
Knight in a previous part of this Book. 

3. The cuttings were taken off in November, and 
not in the spring.* This gave them time to form 

* [Taking off the cuttings in November is unquestionably the 



OF PROPAGATION BY CUTTINGS. 201 

granulations of cellular substance or the lower or 
wounded end, before the powers of absorption by the 
alburnum were aroused, and so to protect themselves 
against a too copious supply cf aqueous matter before 
the growing bud could dispose of it by its leaves 
(64). This protection is afforded by the thinnest 
stratum of new cellular tissue, which covers over the 
ends of the wounded vessels, and acts as a vital filter 
through which all the crude food must pass from the 
soil. 

4. The lower end of the cuttings was so divided as 
to be parallel with the bottom of the pot; and it 
appears from the context, although it is not expressly 
so stated, that this end was to touch the bottom of 
the pot. The importance of this precaution is well 
known ; cuttings of the Lemon and Orange, which 
are by no means willing to strike if it is neglected, 
become young plants readily if it is attended to ; and 
in all difficult cases it is had recourse to. The object 
of it seems to be to place the absorbent or root end 
of the cutting in a situation where, while it is com- 
pletely drained of water, it may, nevertheless, be in 

better practice in so mild a climate as that of England ; and is pre- 
ferable, even in this country, with all very hardy shrubs, as the 
Currant, <fcc But in the case of those which are more tender in the 
bark, as some of the varieties of the common Althaea, the severe 
frost of our winters often seriously injures or destroys the cuttings. 
When of moderate size, they are also liable to be thrown out by the 
heaving of the ground in spring: we therefore generally prefer 
early spring planting, for cuttings. But they often succeed best 
when they are taken off in November, kept in damp mould in the 
cellar through tbe winter, and carefully planted in March or April. 
A. J. D.] 

9* 



202 



APPLICATION OF PRINCIPLES. 



the vicinity of a never-failing supply of aqueous 
vapour. If it were surrounded by earth, water would 
readily collect about it in a condensed state, and the 
vessels being all open in consequence of being cut 
through, would rise at once into the interior ; but 
the application of the root end immediately to the 
earthen bottom of the pot, with which it is so cut as 
to be nearly parallel, necessarily prevents any such 
accumulation and introduction of water, unless over- 
watering is allowed, and this all good gardeners 
will take care to avoid. An ingenious plan of Mr. 
Forsyth's is intended to answer this purpose rather 
more perfectly. He 
puts a small sixty pot 
{fig. 20, a d) into one 
of larger size, having 
first closed up the bot- 
tom of the former with 
clay {a) ; then having 
filled the bottom of the 
outer pot with crocks, 
he rills up the sides 
(c c) with propagating 
soil, in which his cuttings are so placed that their 
root ends rest against the sides of the inner pot ; the 
latter is then filled with water, which passes very 
slowly through the sides until it reaches the cuttings. 
(See Gardener's Magazine, vol. xi. p. 56-4.) In many 
cases, especially in striking such plants as Heaths, 
gardeners employ a stratum of silver sand, placed 
immediately over the earth in which such plants 




OF PKOPAGATION BY CUTTINGS. 203 

love to grow. The cuttings are inserted into the 
sand, but so near the earth that the roots, presently 
after their emission, find themselves in it, and conse- 
quently in contact with a source of food. This sand 
answers the same purpose as placing the root end of 
the cutting in contact with the pot, and is an ingeni- 
ous device for doing that with small cuttings, which 
cannot be conveniently done otherwise except with 
large ones. 

5. The cuttings are eventually placed in a hot- 
bed. This is for the purpose of giving them a stimu- 
lus at exactly that time when they are most ready to 
receive it. Had they been forced at first in bottom 
heat, the stimulus would have been applied to cut- 
tings whose excitability had not been renovated 
(113), and the consequence would have been a deve- 
lopement of the powers of growth so languid, that 
they probably vv'ould not have survived the coming 
winter: but, the stimulus being withheld till the cut- 
tings are quite ready for growth, it tells with the 
utmost possible effect. 

In addition to these comments upon an excellent 
mode of striking cuttings of many kinds, it is neces- 
sary to add some observations upon the object of 
additional precautions often taken by gardeners. 

Cuttings are covered by bell glasses, whose edge is 
pressed into the earth. This is for the purpose of 
preserving a uniform degree of humidity in the 
atmosphere breathed by the cuttings. It is gene- 
rally necessary to leave one or more leaves upon 
a cutting, in order to generate organisable matter, 




204 APPLICATION OF PRINCIPLES. 

and to assist in the formation of roots ; but this is a 
very delicate operation, for, if the leaf is allowed 
to suffer by excessive perspiration, the cuttings must 
necessarily perish (75). To maintain a steady saturat- 
ed atmosphere around a cutting stops this 
danger, and hence the use of a bell glass. A 
double glass has been lately recommended 
(fig. 21) ; but if this precaution is of any 
value, it must be, not because it main- 
tains an even temperature, which is 
injurious rather than useful, but because it prevents 
condensation upon the inner bell glass, and the con- 
sequent abstraction of atmospheric moisture, and pro- 
bably acts at the same time as a kind of shade. 

Notwithstanding the precaution of covering cut- 
tings with a bell glass, shade is also necessary, as a 
further security against perspiration ; for light acts as 
a specific stimulus (71), whose effects are very diffi- 
cult to counteract. It must, howevef, be employed 
with great caution ; for, if there is not light enough, 
the leaves attached to the cuttings cannot form that 
organisable matter out of which roots are produced. 

All gardeners know that the root end of a cutting 
should be dose below a leaf-bud ; this is to facilitate 
the emission of roots by the buds, which emission 
must necessarily take place with greater or less diffi- 
culty in proportion as their exit is facilitated or imped- 
ed by the pressure of bark on them.* 

* [The amateur will find it advantageous to take off the cutting, 
when delicate or short, close up to the main stem, so as to preserve 
the collar or enlarged portion of wood at the base of the branch. 



OF PROPAGATION BY CUTTINGS. 205 

No farther precautions are taken with cuttings, 
nor does it at first sight appear possible to suggest 
any ; nevertheless, the enormous constitutional dif- 
ference among plants is such, that, while numerous 
species will strike without any difficulty under almost 
any circumstances, with the wood ripe or half-ripe, 
just formed or aged, there are many others which no 
art has yet succeeded in converting into plants ; and 
it is by no means uncommon to find that, out of a 
potful of cuttings of the same species, apparently all 
alike and subjected to exactly the same treatment, 
one will grow and the remainder fail. It is, therefore, 
one of the most probable of all things, that the prin- 
ciples of striking cuttings are still very imperfectly 
understood, and that this is one of the points of 
horticulture in which there is the greatest room for 
improvement. 

It may be worthy of inquiry whether bell glasses 
of different colours will not produce different effects 
upon cuttings, in consequence of their different power 
of transmitting light. It has been shown by Dr. 
Daubeny, in a very interesting paper in the Philoso- 
phical Transactions for 1836, page 149, that glass of 
different colours exercises very different effects upon 
the plants exposed to the rays of solar light passing 
through it ; that both the exhalation and absorption 
of moisture by plants, so far as they depend upon the 
influence of light, are affected in the greatest degree 

This consists of a collection of latent buds or fibres, from which 
roots are emitted with much greater facility th an from any other 
portion. A. J. D.] 



206 APPLICATION OF PRINCIPLES. 

by the most luminous rays ; and that all the functions 
of the vegetable economy, which are owing to the 
presence of this agent, follow in that respect the same 
law. In these experiments, it was ascertained that 
the glass employed admitted the passage of the rays 
of light in the following proportions : 



Transparent. 


Orange. 


Red. 


Blue. 


Purple. 


Green. 


Luminous rays 7 


6 


4 


4 


3 


5 


Calorific rays 7 


6 


5 


3 


4 


2 


Chemical rays 7 


4 





6 


6 


3 



M. Decaisne found, during some experiments to 
ascertain the effect of light in causing the production 
of colouring matter in the Madder plant, that when 
the lower parts of a plant were inclosed in cases 
glazed at the side with transparent green, red, or yel- 
low glass, the leaves and stem of the part surrounded 
by red glass became pallid, and exhibited signs of 
suffering in a greater degree than under the other 
colours, but all were affected more or less.* (Recher- 
ches sur la Garance, p. 23.) 

We, however, require very different experiments 
from any yet instituted, before we can proceed to draw 
practical conclusions as to the relative effects upon 
plants of glass of different colours. We do not know 
what the effect is of the calorific and chemical rays, 
and therefore we cannot say what may be the advan- 
tage or disadvantage of their action upon plants. 
As, however, the object of the cultivator is to protect 

* The nature of these experiments has been misapprehended in 
the translation, by Mr. Francis, of Meyen's Report on Vegetable 
Physiology, for 1837, p, 51. 



OF PROPAGATION BY LAYERS AND SUCKERS. 207 

tils cuttings from too much light, and at the same 
time to give them enough to enable them to perform 
their digestive functions steadily, there can be little 
doubt that transparent glass is inferior to that of ano- 
ther colour. 



CHAPTEE XI. 

OF PROPAGATION BY LAYERS AND SUCKERS. 

With regard to layers, there is but little which it 
is necessary to say regarding them, if what has been 
stated respecting eyes, leaves, and cuttings, has been 
rightly understood and well considered. A layer is a 
branch bent into the earth, and half cut through at 
the bend, the free portion of the wound being called 
"a tongue." It is, in fact, a cutting only partially se- 
parated from its parent. 

The object of the gardener is to induce the layer to 
emit roots into the earth at the tongue. With this 
view he twists the shoot half round, so as to injure 
the wood- vessels ; he heads it back so that only a bud 
or two appears above ground ; and, when much nicety 
is requisite, he places a handful of silver sand round 
the tongued part ; then pressing the earth down with 
his foot, so as to secure the layer, he leaves it without 
further care. The intention of both tongueing and 
twisting is to prevent the return of sap from the layer 



208 



APPLICATION OF PRINCIPLES. 



into the main stem, while a small quantity is allowed 
to rise out of the latter into the former ; the effect of 
this being to compel the returning sap to organize it- 
self externally as roots, instead of passing downwards 
below the bark as wood. The bending back is to 
assist in this object, by preventing the expenditure of 
sap in the formation, or rather completion, of leaves ; 
and the silver sand is to secure the drainage so neces- 
sary to cuttings. 

In most cases, this is sufficient ; but it must be 
obvious that the exact manner in which the layering 
is effected is unimportant, and that it may be varied 
according to circumstances. Thus, Mr. James Munro 
describes a successful method of 
layering brittle-branched plants 
by simply slitting the shoot at 
the bend, and inserting a stone 
at that place (Gardener" 1 a Maga- 
zine, ix. 302): and Mr. Knight 
found that, in cases of difficult 
rooting, the process is facilitated 
by ringing the shoot just below 
the tongue, about midsummer, 
when the leaves upon the layers 
had acquired their full growth 
(.Sort Trans., i. 256) ; by which 
means he prevented the passage 
of the returning sap further 
downwards than the point in- 
tended for the emission of roots. 
It will sometimes happen that 




OF PROPAGATION BY LAYERS AND SUCKERS. 209 

the branch of a plant cannot be conveniently bent 
downwards into the earth ; in such cases, the earth 
may be elevated to the branch by various contri- 
vances, as is commonly done by the Chinese, (fig. 
22.) When this is done, no other care is necessary 
than that required for layers, except to keep the earth 
surrounding the branch steadily moist. 

Suckers are branches naturally thrown up by a 
plant from its base, when the onward current of 
growth of the stem is stopped. Every stem, even the 
oldest, must have been. once covered with leaves; 
each leaf had a bud in its axil ; but, of those buds, 
few are developed as branches, and the remainder 
remain latent or perish. When the onward growth of 
a plant is arrested, the sap is driven to find new out- 
lets, and then latent buds are very likely to be deve- 
loped ; in fact, when the whole plant is young, they 
must necessarily shoot forth under fitting circum- 
stances ; the well-known effect of cutting down a tree 
is an exemplification of this. Such branches, if they 
proceed from under ground, frequently form roots at 
their base, when they are employed as a means of 
propagation ; and, in the case of the Pine-apple, they 
are made use of for the same purpose, although they 
do not emit roots till they are separated from the pa- 
rent. Gardeners usually satisfy themselves with tak- 
ing from their Pine-apple plants such suckers as are 
produced in consequence of the stoppage of onward 
growth by the formation of the fruit : but these are 
few in number, and not at all what the plant is 
capable of yielding. Instead of throwing away the 



210 APPLICATION OF PRINCIPLES. 

" stump" of the Pine apple, it should be placed in a 
damp pit, and exposed to a bottom heat of 90° or 
thereabouts, when every one of the latent eyes will 
spring forth, and a crop of young plants be the re- 
sult. Mr. Alexander Forsyth, a very sensible writer 
upon these subjects, pointed this out some years since 
in the Gardener's Magazine (xii. 594) ; and there can 
be no doubt that his observations upon the folly of 
throwing away stumps are perfectly correct both in 
theory and practice. 

The practice of scarring the centre of bulbs, the 
heads of Echinocacti and such plants, and the crown 
of the stem of species like Littsea geminiflora, in all 
which cases suckers are the result, is explicable upon 
the foregoing principles. 



CHAPTER XII. 
OF PROPAGATION BY BUDDING AND GRAFTING. 

These operations consist in causing an eye or a 
cutting of one plant to grow upon some other plant, 
so that the two, by forming an organic union, become 
a new and compound individual. The eye, in these 
cases, takes the name of bud, the cutting is called a 
scion, and the plant upon which they are made to 
grow is named the stock. 

Propagation by eyes and cuttings is, therefore, the 
same as budding and grafting, with this important 



OF PROPAGATION BY BUDDING AND GRAFTING. 211 

difference, that in the one case the fragments of a plant 
are made to strike root into the inorganic soil, and to 
grow on their own bottom, as the saying is, while in 
the other they emit the equivalent of roots into liv- 
ing organic matter. In like manner, the operation of 
inarching, or causing the branch of one plant to 
remain attached to its parent, and at the same time to 
grow upon the branch of another tree, is analogous 
to layering. 

The objects of these operations are manifold. Many 
plants, such as the Pear and the Apple, will bud or 
graft freely, but are difficult to strike from cuttings. 
Species which are naturally delicate become robust 
when "worked" on robust stocks; and the conse- 
quence is a more abundant production of flowers and 
fruit ; thus the more delicate kinds of Vines produce 
larger and finer grapes when worked upon such coarse, 
robust sorts as the Syrian and Nice. The Double 
yellow Rose, which so seldom opens its flowers, and 
which will not grow at all in many situations, blos- 
soms abundantly, and grows freely, when worked 
upon the common China Rose. (See Hort. Trans, v. 
370.) The peculiar qualities of some plants can only 
be preserved by working : this is especially the case 
with certain kinds of variegated Roses, which retain 
their gay markings when budded, but become plain 
if on their own bottom, (lb. 492.) Fruit may be ob- 
tained from seedling plants by these processes much 
earlier than by any others, and thus many years' un- 
certain expectation may be saved : indeed, Mr. Knight 
ascertained that it is possible to transfer the blossom- 



212 



APPLICATION OF PRINCIPLES. 



buds of one plant to another, so as to obtain flowers 
or fruit from them immediately. He thus fixed on 
the Wild Eose the flower-buds of Garden Eoses, 
"and these buds, being abundantly supplied with 
nutriment, afforded much finer roses than they would 
have done had they retained their natural situation." 
He repeated many similar experiments upon the 
Pear and Peach trees with similar success ; but, in 
the case of the Pear, he found that if the buds were 
inserted earlier than the end of August or begin- 
ning of September, they became branches and not 
flowers. 

The manner in which these operations may be 
practised is exceedingly various, and an abundance 
of fanciful methods have been devised, for an account 
of which the reader is referred to Thouin's Mono- 
graphie des Greffes ; to the article " Greffe" by the 
same author, in the Xouveau 
Cours complet oV Agriculture, 
&c, edition of 1822 ; to Lou- 
don's Encyclopaedia of Garden- 
ing, part ii. ; and to the Gar- 
deners Magazine, vol. x. p. 
305. I shall only here de- 
scribe the commoner and more 
important' methods. 

Budding consists in intro- 
ducing a bud of one tree, with 
a portion of bark adhering 
to it, below the bark of ano- 
ther tree. In order to effect 




OF PEOPAGATION BY BUDDING. 213 

this, a longitudinal incision is made through the bark 
of the stock down to the wood, and is then crossed at 
the upper end by a similar cut (fig. 23, <x), so that the 
whole wound resembles the letter T. Then from the 
scion is pared off a bud with a portion of the bark 
(fig. 23, 6), and the latter is pushed below the bark 
of the stock until the bud is actually upon the naked 
wood of the stock ; the upper lips of the wound in 
the stock and that of the bud are made to coincide, 
the whole are fastened down by a ligature, and the 
operation is complete. 

By these means we gain the important end of 
bringing in close contact a considerable surface of 
young organising matter. The organisation of wood 
takes place on its exterior, and that of bark on its 
interior surface, and these are the parts which are 
applied to each other in the operation of budding ; 
in addition to which the stranger bud finds itself, in 
its new position, as freely in communication with ali- 
mentary matter, or more so, than on its parent branch. 
A union takes place of the cellular faces, or horizon, 
tal system, of the stock and bark of the bud, while 
the latter, as soon as it begins to grow, sends down 
the woody matter, or vertical system, through the 
cellular substance. In consequence of the horizontal 
incision, the returning sap of the scion is arrested in 
its course, and accumulates a little just above the new 
bud, to which it is gradually supplied as it is required. 
Sometimes the whole of the wood of the bud below 
the bark is allowed to remain; and, in that case, 
contact between the organising surfaces of the stock 



214 APPLICATION OF PRINCIPLES. 

and scion does not take place, and the union of the 
two is much less certain : as it is, however, usually 
practised with tender shoots before the wood is con- 
solidated, the contact spoken of is of less moment. 
In all cases, a portion of the wood of the bud must 
be left adhering to it, or the bud will perish ; because 
its most essential part is the } r oung woody matter in 
its centre, and not the external surface, which is a 
mere coating of bark.* 

In the Agricultural Journal of the Pays Bas for 
October, 1824, it is recommended to reverse the 
usual mode of raising the bark for inserting the buds, 
and to make the cross cut at the bottom of the slit, 
instead of at the top, as is generally done in Britain. 
The bud is said rarely to fail of success, because it 
receives abundance of the descending sap, which it 
cannot receive when it is under the cross cut. This 
explanation is unintelligible, and there is no ap- 
parent advantage in the method ; it is, however, 
practised by the orange-growers of the South of 
France. 

Mr. Knight was accustomed on some occasions to 
employ two distinct ligatures to hold the bud of his 
Peach trees in its place. One was first placed above 
the bud inserted ; and upon the transverse section 

* [This is the universal opinion, but it is not always practically 
true ; for if the operation be performed at a favorable period, when 
the tree abounds with sap, the space left by extracting the woody 
matter will be almost immediately filled by a new deposit. But 
leaving the wood in the bud, in working fruit-trees, is the general 
and most successful practice, i J. D.] 



OF PROPAGATION BY BUDDING. 



215 



through the back ; the other, which had no further 
office than that of securing the bud, was employed in 
the usual way. As soon as the bud had attached 
itself, the ligature last applied was taken off: but the 
other was suffered to remain. The passage of the 
sap upwards was in consequence 
much obstructed, and buds inserted 
in June began to vegetate strongly 
in July: when these had afforded 
shoots about four inches long, the 
remaining ligature was taken off to 
permit the excess of sap to pass on* 
and the young shoots were nailed to 
the wall. Being there properly ex- 
posed to light, their wood ripened 
well, and afforded blossoms in the 
succeeding spring. 

Flute-budding (fig. 24) is not 
practised in this country, but de- 
serves to be mentioned. It consists 
of peeling off a ring of bark from 
the stock, just below a terminal 
bud; replacing it by a similar ring, 
with a bud or two upon it, taken 

* Nurserymen and others find this tying with double ligatm-e of 
great service in budding the plum. The difficulty in working this 
tree arises from the tendency of the upper part of the bud to curl up 
and detach itself after the ordinary single tie is taken off, and the 
union apparently complete. By leaving on the upper ligature a 
fortnight after the lower one, this tendency to rupture is prevented, 
and the upper bandage may then be removed with safety, and 
before the bud has been excited into growth. A. J. D. 




216 APPLICATION OF PRINCIPLES. 

from a scion ; and binding down the whole. This 
is performed only in the spring, and has the advan- 
tage of being so contrived that the stranger bud 
is placed immediately below that part of a branch 
where processes of organisation are most active, 
namely, below a central bud of the stock ; and from 
occupying all the circumference, it must necessarily 
receive the whole of the alimentary and organised 
matter sent downwards by that bud. It is employed 
in Bavaria for the Mulberry.* (See Gard. Mag. v. 
425.) 

In Grafting no attempt is made to apply the inner 
surface of the bark of a scion to the outer sur- 
face of the wood of the stock ; but the contact 
is effected by the wood of the two, and their 
bark only joins at the edges. Whip-grafting 
(Jig. 25) is the commonest kind ; it is per- 
formed by heading down a stock, then paring 
one side of it bare for the space of an inch 
or so, and cutting down obliquely at the 
upper end of the pared part, towards the pith ; 
the scion is levelled obliquely to a length 
corresponding with the pared surface of the 
stock, and an incision is made into it near 
the upper end of the wound obliquely up- 
wards, so as to form a "tongue," which is 
pil.fi forced into the corresponding wound in the 
« | B stock ; care is then taken that the bark of the 
({"$& scion is exactly adjusted to that of the stocky 
and the two are bound firmly together. 

* [The success of this practice will be found to depend mate- 



i 



m 



OF PROPAGATION BY GRAFTING. 217 

Here the mere contact of the two enables the sap 
flowing upwards through the stock to sustain the life of 
the scion until the latter can develope its buds, which 
then send downwards their wood ; at the same time 
the cellular system of the parts in contact unites by 
granulations ; and, when the wood descends, it passes 
through the cellular deposit, and holds the whole toge- 
ther. The use of " tongueing" is merely to steady the 
scion, and to prevent its slipping. The advantage of 
this mode of grafting is the quickness with which it 
may be performed ; the disadvantage is, that the sur- 
faces applied to each other are much smaller than can 
be secured by other means. It is, however, a great 
improvement upon the old crown-grafting, still em- 
ployed in the rude unskilful practice of some Conti- 
nental gardeners, but expelled from Great Britain ; 
which consists of nothing more than heading down a 
stock with an exactly horizontal cut, and splitting it 
through the middle, into which is forced the end of 
a scion cut into the form of a wedge ; when the whole 
are bound together. In this method the split in the 
stock can hardty be made to heal without great care : 
the union between the edges of the scion and those 

rially upon choosing the exact time or season for performing the 
operation. In some trees, if it be attempted a few days earlier 
or later than a certain period, the operator will experience great 
difficulty in effecting that which might have been done with the 
greatest ease at a more favourable moment The bark of the stock 
should part very readily on introducing the budding-knife; the 
young wood from which the buds are taken should also be in pro- 
per condition, not too young, as it would not hare sufficient consis- 
tency, but just when assuming the appearance of ripening. A. J. D.] 

10 




218 APPLICATION OF PRINCIPLES. 

of the stock is very imperfect, because the bark 
of the former necessarily lies upon the wood of 
the latter, except just at the sides; and, from the 
impossibility of bringing the two barks in contact, 
neither the ascending nor descending cur- 
rents of sap are able freely to intermin- 
gle. This plan, much improved by cut- 
ting out the stock into the form of a wedge, 
instead of splitting it, may, however, be 
advantageously employed for such plants 
as Cactacese {fig. 26), the parts of which, 
owing to their succulence, readily form a 
union with each other. 
A far better method than whip-graft- 2 ? 

ing, but more tedious, is saddle-graft- 
ing (fig. 27) ; in which the stock is 
pared obliquely on both sides till it be- 
comes an inverted wedge, and the scion 
is slit up the centre, when its sides are 
pared down till they fit the sides of 
the stock. In this method, the great- 
est possible quantity of surface is 
brought into contact, and the parts are 
mutually so adjusted, that the ascend- 
ing sap is freely received from the 
stock by the scion, while, at the same 
time, the descending sap can flow 
freely from the scion into the stock. 
Mr. Knight, in describing this mode of operating, has 
the following observations : 

" The graft first begins its efforts to unite itself to 



OF PROPAGATION BY GRAFTING. 



219 



the stock just at the period when the formation of a 
new internal layer of bark commences in the spring ; 
and the fluid which generates this layer of bark, and 
which also feeds the inserted graft, radiates in every 
direction from the vicinity of the medulla to the 
external surface of the alburnum. The graft is, of 
course, most advantageously placed when it presents 
the largest surface to receive such fluid, and when 
the fluid itself is made to deviate least from its natu- 
ral course. This takes place most efficiently when 
(as in this saddle-grafting) a graft of nearly equal size 
with the stock is divided at its base and made to 
stand astride the stock, and when the two divisions 
of the graft are pared 
extremely thin, at and 
near their lower extre- 
mities, so that they 
may be brought into 
close contact with the 
stock (from which but 
little bark or wood 
should .be pared off) i 
by the ligature." (HbrtA 
Trans, v. 147.) To ex- 
ecute saddle-grafting] 
properly, the scion andl 
stock should be of 
equal size : and, where 
that cannot be ; a se- 
cond method, in which I 
the scion may be much I 




220 APPLICATION OF PRINCIPLES. 

smaller than the stock, has been described by the 
same great gardener. This {fig. 28) is practised 
upon small stocks almost exclusively in Here- 
fordshire; but it is never attempted till the usual 
season of grafting is past, and till the bark is rea- 
dily detached from the alburnum. The head of 
the stock is then taken off, by a single stroke of 
the knife, obliquely, so that the incision commences 
about the width of the diameter of the stock below 
the point where the medulla appears in the section, 
and ends as much above it, upon the opposite side. 
The scion, or graft, which should not exceed in dia- 
meter half that of the stock, is then to be divided 
longitudinally, about two inches upwards from its 
lower end, into two unequal divisions, by passing the 
knife upwards, just in contact with one side of the 
medulla. The stronger division of the graft is then 
to be pared thin at its lower extremity, and intro- 
duced, as in crown -grafting, between the bark and 
wood of the stock ; and the more slender division is 
fitted to the stock upon the opposite side. The graft, 
consequently, stands astride the stock, to which it 
attaches itself firmly upon each side, and which 
it covers completely in a single season. Grafts of 
the Apple and Pear rarely ever fail in this method 
of grafting, which maybe practised with equal success 
with young wood in July, as soon as it has become 
moderately firm and mature." 

* A very neat and satisfactory mode of propagating fruit trees 
when large stocks are not at hand, is to take small pieces of the 
roots of the proper kinds of stocks and graft the scion9 on these 



OF PROPAGATION BY GRAFTING. 221 

In all these methods, and in every other that could 
be named, it is indispensable that similar parts should 
be brought as much as possible into contact ; for the 
more completely this is accomplished, the more cer- 
tain is the operation to succeed. It is undoubtedly 
true, that, as the cellular system of a tree is diffused 
through its whole diameter (43, 46), it is impossible 
to apply a scion to a stock without their cellular sys- 
tems coming in contact ; and, therefore, it might ap- 
pear indifferent whether bark is applied to bark and 
alburnum to alburnum, or whether the bark is adapt- 
ed to the wood and the latter to the liber. But it is 
always to be remembered that each of these parts has 
special modifications of its own, which modifications 
require contact with parts similarly modified, in or- 
der to unite readily and firmly ; and also, that, al- 

roots, by common whip grafting. Then plant them at once, cover- 
ing the point of union about two inches under the surface of the 
soil. Small seedling apple stocks, one year old, even if only the 
thickness of the graft, answer perfectly well in this manner. 

The apple tree is propagated in American nurseries, by millions 
every year, by grafting the roots, or rather the stocks headed down 
to an inch or so above the crown of the root, splitting them, and 
inserting the scion sloped to a wedge shape in the common mode of 
cleft grafting. The two year seedling stocks used for this purpose, 
are usually lifted in the autumn, and buried in a cellar for this pur- 
pose. The grafts are inserted in winter by the fire-side ; when 
grafted, the scion is held firm by a bit of matting bound round the 
stock, the latter is then packed away in the cellar till spring. Then 
the grafts are planted out in rows in the nursery, and by autumn 
they have grown from three to six feet high. As the earth covers 
the graft-wound no grafting clay or wax is needed, and the whole, 
except planting, is done in winter, when labor is least valuable. 

A J. D, 



222 APPLICATION OF PRINCIPLES. 

though the cellular horizontal system, through which 
union by the first intention takes place, may be alive 
on all parts of the section of a branch, yet that it is in 
the bark, and in the space between the bark and 
wood, that its developement is most rapid, and its 
tendency to growth most easily excited and main- 
tained. 

It is not, however, to be supposed that these opera- 
tions can be performed indifferently, between any two 
species, although such was formerly so general a 
belief that it was asserted that roses became black 
when grafted on Black Currants, and oranges crim- 
son if worked on the Pomegranate.* In point of 
fact, the operations are successful in those cases only 
where the stock and scion are very nearly allied ; and 
the degree of success is in proportion to the degree of 
affinity. Thus, varieties of the same species unite the 
most freely, then species of the same genus, then 
genera of the same natural order ; beyond which the 
power does not extend, unless, in the case of parasites 
like the Mistletoe, which grow indifferently upon 
totally different plants. For instance, Pears work 
freely upon Pears, very well on Quinces, less willing- 
ly on Apples or Thorns, and not at all upon Plums 
or Cherries ; while the Lilac will take on the Ash, 
and the Olive on the Phillyrea, because they are 
plants of the same natural order. M. De Candolle 

* Et steriles platani malos gessere, yalentes 
Castaneae fagos, ornusque incanuit albo 
Flore pyri, glandemque sues fregere sub ulmis. 

Georg. lib. ii. 



OF PROPAGATION BY GRAFTING. 223 

even says that lie has succeeded, notwithstanding the 
great difference in their vegetation, to work the Lilac 
on the Phillyrea, the Olive on the Ash, and the 
Bignonia radicans on the Catalpa ; but plants so ob- 
tained are very short-lived. For some curious parti- 
culars upon this subject, see Physiologic Vegetate , p. 
788, &c. 

There are two cases apparently at variance with 
this law ; both of which require explanation. 

1. Columella asserts that, by a particular manner 
of grafting, the Olive may be made to take upon the 
Fig tree, and his words have been repeated by many 
writers ; but Thouin proved, experimentally, that no 
such union will take place, and that where success 
appears to attend Columella's operation, it is owing 
to the scion rooting into the soil, independently of 
the Fig stock (see Memoire sur la pretendue Ghreffe 
Oolumelle), and becoming a layer. 

2. Mention is made by Pliny of a tree in the gar- 
den of Lucullus, which was so grafted as to bear pears, 
apples, figs, plums, olives, almonds, grapes, &c. ; and 
at this day the gardeners of Italy, especially of Genoa 
and Florence, sell plants of Jasmines, Roses, Honey- 
suckles, &c, all growing together from a stock of 
Orange, or Myrtle, or Pomegranate, on which they 
say they are grafted. But this is a mere cheat, the 
fact being that the stock has its centre bored out, so 
as to be made into a hollow cylinder, through which 
the stems of Jasmines and other flexible plants are 
easily made to pass, their roots intermingling with 
those of the stock ; after growing for a time, the hori- 



224 APPLICATION OF PRINCIPLES. 

zontal distension of the stems forces them together, 
and they assume all the appearances of being united. 
Such plants are, of course, very short-lived. 

From what has been now stated, it may be easily 
conceived that the choice of the stock on which a 
given plant is to be worked is by no means a matter 
of indifference, but that the operation may be serious- 
ly affected by the skill with which the most suitable 
stock is selected. If, indeed, we had no other object 
in view in grafting than to unite one plant to ano- 
ther, that object Avould doubtless be best attained by 
using the same species, and even a similar variety of 
the same species, for both stock and scion ; the ends 
of grafting and budding are, however, much beyond 
this, and it often happens that the species to which a 
scion belongs, or the nearest variety, is the worst on 
which it can be worked. It is, indeed, sometimes 
asserted that the stock exercises little influence over 
the scion, but this is so great an error that it cannot 
be too distinctly contradicted. This subject has al- 
ready been adverted to, but it now requires more 
special consideration. 

One of the first objects of budding and grafting, is 
to multiply a given species or variety more readily 
than is possible by any other method. If this is the 
only purpose of the cultivator, that stock will obvi- 
ously be the best which can be most readily procur- 
ed ; and hence we see, in the ordinary practice of the 
nurseries, the common Plum taken as a stock for 
Peaches and Apricots, the "Wild Pear and Crab for 
Pears and Apples, and so on. When there is a dim- 



OF PROPAGATION BY GRAFTING. 225 

culty in procuring a suitable stock, pieces of the roots 
of the plant to be multiplied are often taken as a sub- 
stitute, and they answer the purpose perfectly well ; 
for the circumstance which hinders the growth of 
pieces of a root into young branches is merely their 
want of buds : if a scion is grafted upon a root, that 
deficiency is supplied, and the difference between the 
internal organisation of a root and a branch is so 
trifling as to oppose no obstacle to the solid union of 
the two. 

Mr. Knight was the first to show the possibility of 
grafting scions upon roots. An account of his me- 
thod of doing this was given at a very early period 
of the existence of the Horticultural Society (June, 
1811), and he at the same time suggested the possibi- 
lity of the practice being applied to grafting scarce 
herbaceous plants upon the roots of their commoner 
congeners ; an operation now commonly practised 
with the Dahlia, Pa^ony, and other plants of a similar 
kind ; and lately a method of multiplying Combre- 
tum purpureum by similar means has been pointed 
out in the Proceedings of the Horticultural Society, i. 
40. 

Mere propagation is, however, by no means the 
only object of the grafter ; another and still more im- 
portant one is, to secure a permanent union between 
the scion and stock, so that the new plant may grow 
as freely and as long as if it were on its own bottom 
under the most favourable circumstances. If this is 
not attended to, the hopes of the cultivator will be 
frustrated by the early death of his plant. 
10* 



226 APPLICATION OF PRINCIPLES. 

Whenever the stock and graft or bud are not per- 
fectly well suited to each other, an enlargement is 
well known always to take place at the point of their 
junction, and generally to some extent either above 
or below it. This is particularly observable in Peach 
trees which have been budded, at any considerable 
height from the ground, upon Plum stocks ; and it 
appears to arise from the obstruction which the de- 
scending sap of the Peach tree meets with in the bark 
of the Plum stock ; for the effects produced, both 
upon the growth and produce of the tree, are simi- 
lar to those which occur when the descent of the 
sap is impeded by a ligature, or by the destruc- 
tion of a circle of bark. In course of time this 
difference between the scion and stock puts an 
end to the possibility of the ascending and de- 
scending fluids passing into each other, and the 
death of the scion is the result. In all the cases I 
have seen, this has arisen from the power of hori- 
zontal growth in the stock and scion being different ; 
and I doubt whether it ever proceeds from any other 
cause. For example : the Hawthorn and the Pear 
are so nearly allied that the latter may be easily work- 
ed upon the former; the Hawthorn is, however, a 
slow-growing bush or small tree ; the Pear is a large 
forest tree of rapid growth ; and the Pear will grow 
an inch in diameter while the Hawthorn is growing 
half an inch. 

This last circumstance, if the difference in the rate 
of growth or in other respects is not excessive, may 
be taken advantage of for particular purposes. When 



OF PROPAGATION BY GRAFTING. 227 

trees grow too large for a small garden, it is desirable 
to dwarf them; and when they are naturally unfruit- 
ful, to render them productive: both which effects 
result, at the same time, from grafting them upon 
stocks that grow slower than themselves. Thus the 
Apple is dwarfed by grafting on the Paradise stock, 
and the Pear by the Quince. The physiological ex- 
planation of trees dwarfed by being compelled to 
grow upon a stock which compels their descending 
sap to accumulate in the branches has been already 
given (85). Instead of repeating it here, I take the 
following paragraph from the paper by Mr. Knight, 
" On the Effects of Different Kinds of Stocks in Graft- 
ing," published in the Horticultural Transactions, ii. 
199. 

"The disposition in young trees to produce and 
nourish blossom buds and fruit is increased by this 
apparent obstruction of the descending sap ; and the 
fruit of such young trees ripens, I think, somewhat 
earlier than upon other young trees of the same age, 
which grow upon stocks of their own species ; but 
the growth and vigour of the tree, and its power to 
nourish a succession of heavy crops, are diminished, 
apparently, by the stagnation, in the branches and 
stock, of a portion of that sap which, in a tree grow- 
ing upon its own stem, or upon a stock of its own 
species, would descend to nourish and promote the 
extension of the roots. The practice, therefore, of 
grafting the Pear tree on the Quince stock, and the 
Peach and Apricot on the Plum, where extensive 
growth and durability are wanted, is wrong ; but it is 



228 APPLICATION OF PRINCIPLES. 

eligible wherever it is wished to diminish the vigour 
and growth of the tree, and where its durability is 
not thought important. 

" When," adds this great gardener, "much diffi- 
culty is found in making a tree, whether fructiferous 
or ornamental, of any species or variety, produce 
blossoms, or in making its blossoms set when pro- 
duced, success will probably be obtained in almost all 
cases by budding or grafting on a stock which is 
nearly enough allied to the graft to preserve it alive 
for a few years, but not permanently. The Pear tree 
affords a stock of this kind to the Apple ; and I have 
obtained a heavy crop of Apples from a graft which 
had been inserted in a tall Pear stock only twenty 
months previously, in a season when every blossom 
of the same variety of fruit in the orchard was destroy- 
ed by frost. The fruit thus obtained was externally 
perfect, and possessed all its ordinary qualities ; but 
the cores were black and without a single seed ; and 
every blossom had certainly fallen abortively, if it 
had been growing upon its native stock. The expe- 
rienced gardener will readily anticipate the fate of the 
graft ; it perished in the following winter. The stock, 
in such cases as the preceding, promotes, in propor- 
tion to its length, the early bearing and early death 
of the graft." 

It is sometimes desirable to increase the hardiness 
of a variety, and grafting or budding appears to pro- 
duce this effect to a certain extent, not, indeed, by 
the stock communicating to the scion any of its own 
power of resisting cold, but by the stock being better 



OF PROPAGATION BY GRAFTING. 229 

suited to the soil of latitudes colder than that from 
which the scion comes, and consequently requiring a 
lower bottom-heat to arouse its excitability. Mr. 
Knight, indeed, denies the fact, because "the root 
which nature gives to each seedling plant must be 
well, if not best, calculated to support it ;" and it is so, 
under the circumstances in which the species was first 
created ; but, without this addition, the paragraph 
quoted in inverted commas is specious only, not just. 
Probably, in Persia, the native country of the Peach, 
that species, or its wild type the Almond, is the best 
stock for the former fruit ; because the temperature 
of the earth (see 117, 118, 119, and Book II. Ch. I.) 
is that in which it was created to grow. But in a 
climate like that of England, the temperature of 
whose soil is so much lower than that of Persia, the 
Plum, on which the Peach takes freely, is a hardy 
native, and suited to such soil, and its roots are 
aroused from their winter sleep by an amount of 
warmth unsuited to the Peach. And experience, in 
this case, completely confirms what theory teaches ; 
for, although there may be a few healthy trees 
in this country growing upon Almond stocks, it is 
perfectly certain that the greater part of those which 
have been planted have failed ; while, in the warm 
soil of France and Italy, it is the stock upon which 
the old trees have, in almost all cases, been budded. 

In determining upon what kind of stock a given 
fruit tree should be grafted, it is important to be 
aware that certain species prefer particular soils and 
dislike others, for reasons which are not susceptible 



230 APPLICATION OF PRINCIPLES. 

of explanation. In the case of the common stocks 
employed for the propagation of the Apple, Pear, 
Peach, and Cherry, it was found by Mr. Dubreuil, 
an intelligent gardener at E-ouen, that in the chalky 
gardens about that city neither the Plum nor the 
wild Cherry would succeed for stone fruit, nor the 
Doucin or Quince stock for Pears and Apples ; but 
that the Crab suited the Apple, the wild Pear the 
cultivated Pear, the Almond the Peach, and the Ma- 
haleb the Cherry. I formerly witnessed the result of 
those experiments while in progress, and I well 
remember the sickly state of his peaches and Cherries 
grafted on Plum and Cherry stocks in the calcareous 
borders of the rampart gardens of Rouen, and the 
healthiness of the same fruit trees in the same garden, 
when worked upon the Almond and the Mahaleb, 
while the latter were unhealthy in their turn in the 
borders composed artificially of loam. The result 
of this experiment has been mentioned in the Hort 
Trans.., iv. 566, and is as follows : — 





Loamy Soil. 


Chalky. 


Light.* 


Apple 


Doucin 


Crab 


Doucin. 


Pear 


Quince 


Wild Pear 


Quince. 


Plum 


Pluni 


Almond 


Almond. 


Cherry- 


Wild Cherry 


Mahaleb 


Wild Cherry.t 



As this work treats exclusively of those operations 
in gardening which can be explained upon known 

* That is, with an admixture of sand and decayed vegetable 
matter. 

f By Wild Cherry here is meant Mazzard, and not our Wild Cherry. 
A J. D. 



OF PROPAGATION BY GRAFTING. 231 

principles of vegetable physiology, all further refer- 
ence to the question of stocks ought, in strictness, to 
be dismissed at this stage. It may be as well, however, 
to add that there are some well-attested facts relating 
to the preference of particular varieties for one kind 
of stock rather than another, which we cannot explain, 
but which are so important in practice as to deserve 
to be studied carefully. There appears to be no 
doubt that, as is asserted by Mr. Knight and others 
(ffort. Trans., ii. 215 ; Gard. Mag., vii. 195), the Apri- 
cot succeeds better on its own species than on the 
Plum. The nurserymen know very well that what 
they call French Peaches, such as the Bourdine, Belle 
Chevreuse, and double Montague, will only take on 
the Pear Plum, while other varieties prefer the 
Muscle Plum; and a variety called the Brompton 
suits them all equally well, making handsome trees, 
which are, however, uniformly short-lived.* The 
Lemon is also found to be a better stock for the 
Orange than its own varieties. 

It is not merely upon the productiveness or vigour 
of the scion that the stock exercises an influence ; its 
effects have been found to extend to the quality of 
the fruit. This may be conceived to happen in two 
ways — either by the ascending sap carrying up with 
it into the scion a part of the secretions of the stock, 
or by the difference induced in the general health of 
a scion by the manner in which the flow of ascending 
and descending sap is promoted or retarded by the 

* See G. Lindley's Guide to the Orchard and Kitchen Garden, p. 



232 APPLICATION OF PRINCIPLES. 

stock. In the Pear, the fruit becomes lighter coloured 
and smaller on the Quince stock, than on the wild 
Pear, still more so on the Medlar ; and in these two 
instances the ascent and descent of sap is obstructed 
by the Quince more than by the wild Pear, and by 
the Medlar more than by the Quince. Similar effects 
are produced in the Apple by the Paradise and Sibe- 
rian Bittersweet stocks. Mr. Knight mentions such 
differences in the quality of his Peaches. His garden 
contained two trees of the Acton Scott variety, "one 
growing upon its native stock, the other upon a Plum 
stock, the soil being similar and the aspect the same. 
That growing upon the Plum stock, afforded fruit of a 
larger size, and its colour, where it was exposed to the 
sun, was much more red; but its pulp was more 
coarse, and its taste and flavour so inferior that he 
would have denied the identity of the variety, had he 
not with his own hand inserted the buds from which 
both sprang." (Rort. Trans., v. 289.) 

In addition to a judicious adaptation of the bud or 
scion to the stock, there are other circumstances to 
which it is necessary to attend, in order to insure the 
success of the operation. It has already been seen 
(p. 180), that the youngest buds of the Potato are more 
excitable than those more completely matured ; and 
the same appears to be true of the bud in other fruits. 

" The mature bud," says Mr. Knight, " takes imme- 
diately with more certainty, under the same external 
circumstances : it is much less liable to perish during 
winter ; and it possesses the valuable property of 
rarely or never vegetating prematurely in the sum- 



OF PROPAGATION BY GRAFTING. 233 

mer, though it be inserted before the usual period, 
and in the season when the sap of the stock is most 
abundant. I have, in different years, removed some 
hundred buds of the Peach tree from the forcing- 
house to luxuriant shoots upon the open wall ; and I 
have never seen an instance in which any of such 
buds have broken and vegetated during the summer 
and autumn ; but when I have had occasion to 
reverse this process and to insert immature buds from 
the open wall into the branches of trees growing in a 
Peach-house, many of these, and in some seasons all, 
have broken soon after being inserted, though at the 
period of their insertion the trees in the Peach-house 
had nearly ceased to grow." (Horl. Trans., iii. 136.) 

This property was turned to practical account by 
Mr. Knight in budding the Walnut. Owing to the 
excitability of its buds, this tree is difficult to work, 
because its buds exhaust all their organisable and ali- 
mentary matter before any adhesion can be formed 
between themselves and the stock ; but by taking the 
small, fully matured, and little developed buds, found 
at the base of the annual shoots of this plant, time is 
given for an adhesion between them and the albur- 
num before they push forth, and then they take freely 
enough. (See Hort. Trans. , iii. 135.) 

Buds should either be inserted when the vegeta- 
tion of a plant is languid, or growth above the place 
of insertion should be arrested by pinching the ter- 
minal bud ; otherwise the sap, which should be 
directed into the bud, in order to assist in its adhe- 
sion, is conveyed to other places, and the bud 



234 APPLICATION OF PRINCIPLES. 

perishes from starvation. For similar reasons, when 
a bud begins to grow, having firmly fixed itself npon 
the stock, the latter should be headed back nearly as 
far as the bud, so as to compel all the ascending cur- 
rent of sap to flow towards it ; otherwise the buds of 
the stock itself will obtain that food which the 
stranger bud should be supplied with. 

In grafting also it is always found that a union be- 
tween the scion and the stock takes place most readily 
when the latter is headed down ; but this is not the only 
point to attend to. The scion should always be so pre- 
pared that a bud is near the point of union between 
itself and the stock, because such a bud, as soon as it 
begins to grow, proceeds to furnish wood which assists 
in binding the two together. The scion should be more 
backward in its vegetation than the stock, because 
it will then be less excitable ; otherwise its buds may 
begin to grow before a fitting communication is esta- 
blished between the stock and scion, and the latter 
will be exhausted by its own vigour : if, on the con- 
trary, the stock is in the state of incipient growth, and 
the scion torpid, granulations of cellular tissue will 
have time to form and unite the wound, and the scion 
will become distended with sap forced into it from 
the stock, and thus be able to keep its buds alive 
when they begin to shoot into branches. In order to 
assist in this part of the operation, a " heel" is some- 
times in difficult cases left on a scion, and inserted 
into a vessel of water, until the .union has taken 
place ; or, for the same purpose, the scion is bound 
round with loose string or linen with one end steeped 



OF PROPAGATION BY GRAFTING. 235 

in water, so as to secure a supply of water to the 
scion by the capillary attraction of such a bandage. 
Indeed, the ordinary practice of surrounding the 
scion and stock at the point of contact with a mass of 
grafting clay is intended for the same purpose ; that 
is to say, to prevent evaporation from the surface of 
the scion, and to afford a small supply of moisture ; 
and hence, among other things, the superiority of 
clay over the plasters, mastics, and cements, occasion- 
ally employed, which simply arrest perspiration, and 
can never assist in communicating aqueous food to 
the scion. 

Here also must be noticed certain practices, which 
experience shows to be important, of which theory of- 
fers no obvious explanation. Mr. Knight, for exam- 
ple, asserts that cuttings taken from the trunks of 
seedling old trees grow much more vigorously than 
those taken from the extremities of bearing branches ; 
and it is an undoubted fact that the Beech, and other 
trees of a similar kind, cannot be grafted with any 
success, unless the scions are made of two-years'-old 
wood ; one-year-old wood generally fails. 

What is called herbaceous grafting, or Tschudy 
grafting, depends so entirely upon the same princi- 
ples as common grafting, that a separate notice of it 
is hardly necessary. Nevertheless, as it is sometimes 
very useful, a few words may be given to it. When 
two vigorous branches cross each other, and press 
together, so as not to move, they will often form an 
organic union ; if two apples press together, or if two 
cucumbers are forced to grow side by side in a space 



236 APPLICATION OF PRINCIPLES. 

so small as to compel tliem to touch each other firmly, 
they also will grow together ; and herbaceous graft- 
ing is merely an application to practice of this power 
of soft and cellular parts to unite. In order to secure 
success, the scion and stock, being pared so as to fit 
together accurately, are firmly bound to each other, 
without being crushed ; parts in full vegetation, and 
abounding in sap, are always chosen for the opera- 
tion, such as the upper parts of annual shoots, near 
the terminal bud ; perspiration is diminished by the 
removal of some of the leaves of both stock and scion, 
and by shading (71) ; and b} r degrees, as the union 
becomes secured, buds and leaves are removed from 
the stock, in order that all the sap possible may be 
impelled into the scion. This method, if well managed, 
succeeds completely in about thirty days, and is use- 
ful as a method of multiplying lactescent, resinous, 
and hard-wooded trees, which refuse to obey more 
common methods. Baron de Tschudy succeeded in 
this way in working the Melon on the Bryony (both 
Cucurbitaceous plants), the Artichoke on the Car- 
doon (both Cynaras), Tomatoes on Potatoes (both 
Solanums), and so on. The following account of 
managing Conifers, where herbaceous grafting is 
used, is taken from the Gardener's Magazine, vol. ii. 
p. 64, and sufficiently explains the practice : — 

"The proper time for grafting pines is when the 
young shoots have made about three quarters of their 
length, and are still so herbaceous as to break like a 
shoot of asparagus. The shoot of the stock is then 
broken off about two inches under its terminating 



OF PROPAGATION BY GRAFTING. 



237 



bud ; the leaves are stripped off from twenty to 
twenty -four lines down the extremity, leaving, how- 
ever, two pairs of leaves opposite, and close to the 
section of fracture, which leaves are of great import- 
ance. The shoot is then split with a very thin knife 
between the two pairs of leaves {fig. 29, a,) and to 
the depth of two inches. The scion is then prepared 
(b) : the lower part, being stripped of its leaves to the 
length of two inches, is 29 

cut, and inserted in the 
usual manner of cleft- 
grafting. They may also 
be grafted in the lateral 
manner (c.) The graft is 
tied with a slip of woollen, 
and a cap of paper is put 
over the whole, to protect 
it from the sun and rain. 
At the end of fifteen days 
this cap is removed, and 
the ligature at the end of 
a month ; at that time also 
the two pairs of leaves (a), which have served as 
nurses, are removed. The scions of those sorts of 
pines which make two growths in a season, or, as 
the technical phrase is, have a second sap, produce a 
shoot of five or six inches in the first year ; but those 
of only one sap, as the Corsican Pine, Weymouth Pine, 
&c, merely ripen the wood grown before grafting, and 
form a strong terminating bud, which in the following 
year produces a shoot of fifteen inches, or two feet." 




238 



APPLICATION OF PRINCIPLES. 



With regard to inarching, which, was probably 
the most ancient kind of grafting, because it is that 
which must take place accidentally in thickets and 
forests, it differs from grafting in this, that the scion 
is not severed from its parent, but remains attached 
to it until it has united to the stock to which it is tied 
and fitted in various ways ; the scion and stock are 
therefore mutually independent of each other, and 
the former lives upon its own resources, until the union 
is completed. 

In practice, a portion of the branch of a scion 
is pared away, well down into the alburnum ; a cor- 
responding wound is made in the branch of a stock ; 
tongues are made in each wound so that they will fit 
into each other ; and the liber and al- 
burnum of the two being very accu- 
rately adjusted, the whole are firmly 
bound up ; grafting clay is applied to 
the wound, and the plants operated 
upon are carefully shaded; in course 
of time the wounds unite, and then 
the scion is severed from its parent. 
Gardeners consider this the most cer- 
tain of all modes of grafting, but it is 
troublesome, and only practised in dif- 
ficult cases. The circumstances most 
conducive to its success are, to stop the 
branch of both stock and scion under 
operation, so as to obtain an accumula- 
tion of sap, and to arrest the flow of sap 
upwards; to moderate the motion of 




OF PRUNING. 239 

the fluids by shading ; to head back the stock as far 
as the origin of the scion, as soon as the union is 
found to be complete ; and at the same time to re- 
trench from the scion a part of its buds and leaves, so 
that there may not be a too rapid demand upon the 
stock, while the line of union is still imperfectly con- 
solidated. 

A method of propagating Camellias, {fig. 30,) by 
putting the end or heel of a scion into a vessel of 
water, mentioned in the Gardeners Magazine, ii. 33, 
is essentially the same as inarching. The water 
communicated to the scion through the wounded end 
supplies it with that food which, under natural cir- 
cumstances, would be derived from the roots of the 
plant to which it belongs.* 



CHAPTEE XIII. 

OF PRUNING. 

"La taille est une des operations les plus import- 
antes et les plus delicates du jardinage. Confie'e 

* One of our most experienced gardeners propagates the camellia 
with great facility, by whip grafting small seedling stocks and 
plunging the pots in the hone-black of the sugar refineries, covering 
the graft entirely with this fine loose material. This not only pre- 
serves an uniform state of moisture about the graft, but it seems to 
exert some specific action upon the growth of new wood, doubtless 
from the action of the phosphate of lime in the bone-black. The 
luxuriance of the young grafts raised in this way is very remark- 
able. A. J. D. 



240 APPLICATION OF PRINCIPLES. 

commundraent a des ouvriers peu instruits, observe 
dans les resultats d'une pratique trop souvent irre- 
flechie, elle a du necessairement trouver des detrac- 
teurs meme parmi les physiologistes. II en eut sans 
doute ete autrement, si onravaitetudieedanslesjardins 
du petit nombre de praticiens qui ont su de nos jours 
la bien comprendre. Sagement basee sur les lois de 
la vegetation, elle contribue, entre leurs mains, non 
seulement a regulariser la production des fruits, a en 
obtenir de plus beaux, mais encore a prolonger l'ex- 
istence et la fecondite des arbres." 

Nothing can be more just than these words, 
addressed to the Horticultural Society of Paris, by 
their President, M. Hericart de Thury ; and, if they 
do not apply with as much force to our gardeners as 
to those of France, the}' do most fully to our forest- 
ers. 

The quantity of timber that a tree forms, the 
amount and quality of its secretions, the brilliancy of 
its colours, the size of its flowers, and, in short, its 
whole beauty, depend upon the action of its branches 
and leaves, and their healthiness (64). The object of 
the pruner is to diminish the number of leaves and 
branches ; whence it may be at once understood how 
delicate are the operations he has to practise, and how 
thorough a knowledge he ought to possess of all the 
laws which regulate the action of the organs of vege- 
tation. If well directed, pruning is one of the most 
useful, and, if ill- directed, it is among the most mis- 
chievous, operations that can take place upon a 
plant. 



OF PRUNING. 241 

When a portion of a healthy plant is cut off, all 
that sap Avhich would have been expended in sup- 
porting the part removed is directed into the parts 
which remain, and more especially into those in the 
immediate vicinity of it. Thus, if the leading bud of 
a growing branch is stopped, the lateral buds, which 
would otherwise have been dormant, are made to sprout 
forth ; and, if a growing branch is shortened, then 
the very lowest buds, which seldom push, are brought 
into action : hence the necessity, in pruning, of cut- 
ting a useless branch clean out ; otherwise the remo- 
val of one branch is only the cause of the production 
of a great many others. This effect of stopping does 
not always take place immediately; sometimes its 
first effect is to cause an accumulation of sap in a 
branch, which directs itself to the remaining buds, 
and organises them against a future year. In ordi- 
nary cases, it is thus that spurs or short bearing- 
branches are obtained in great abundance. The 
growers of the Filbert, in Kent, procure in this way 
greater quantities of bearing wood than nature unas- 
sisted would produce ; for, as the filbert is always 
borne by the wood of a previous year, it is desirable 
that every bush should have as much of that wood as 
can be obtained, for which everything else may be 
sacrificed; and such wood is readily secured by 
observing a continual system of shortening a young 
branch by two thirds, the effect of which is to call 
all its lower buds into growth the succeeding year ; 
and thus each shoot of bearing wood is compelled to 
produce many others. The Peach, by a somewhat 
11 



242 APPLICATION OF PRINCIPLES. 

similar system, has been made to bear fruit in unfa- 
vourable climates (Hort. Trans. , ii. 366) ; and every 
gardener knows bow universally it is applied to the 
Pear, Apple, Plum, and similar trees.* Even the 
Fig-tree has thus been rendered much more fruitful 
than by any other method. " Whenever," says Mr. 
Knight, " a branch of this tree appears to be extending 
with too much luxuriance, its point, at the tenth or 
twelfth leaf, is pressed between the finger and 
thumb, without letting the nails come in contact with 
the bark, till the soft succulent substance is felt to 
yield to the pressure. Such branch, in consequence, 
ceases subsequently to elongate ; and the sap is 
repulsed, to be expended where it is more wanted. 
A fruit ripens at the base of each leaf, and during the 
period in which the fruit is ripening, one or more of 
the lateral buds shoots, and is subsequently sub- 
jected to the same treatment, with the same result. 
When I have suffered such shoots to extend freely to 
their natural length, I have found that a small part 
of them only became productive, either in the same 

[* Nothing is more general, of late years, than complaints of the 
short period of productiveness in the Peach tree, throughout the 
Middle States. Although this is often owing to the worm, which 
girdles the tree at the root, yet the almost total neglect of pruning 
is a frequent cause of sterility and decay. When left to itself the 
interior of the head of the tree becomes filled with small dead 
branches, and the trunk and larger limbs bark -bound and moss- 
covered: the whole tree is enfeebled ; leaves are only produced at 
the extremity of the long branches, and the fruit borne, if any, is 
comparatively worthless. By pursuing the practice recommended 
in the text, the trees may be preserved for a long time in a high 
state of vigour and productiveness. A J. D.] 



OF PRUNING. 243 

or the ensuing season, though I have seen that their 
buds obviously contained blossoms. I made several 
experiments to obtain fruit in the following spring 
from other parts of such branches, which were not 
successful; but I ultimately found that bending 
these branches, as far as could be done without danger 
of breaking them, rendered them extremely fruitful ; 
and, in the present spring, thirteen figs ripened per- 
fectly upon a branch of this kind within the space 
of ten inches. In training, the ends of all the shoots 
have been made, so far as practicable, to point down- 
wards." (Sort. Trans., iv. 201.) 

The effect produced upon one part by the abstrac- 
tion of some other part, thus shown in the develope- 
ment of buds which would otherwise be dormant, is 
seen in many other ways. If all the fruit of a plant 
is abstracted one year when just forming, the fruit 
will be finer and more abundant the succeeding year, 
as happens when late frosts destroy our crops. If of 
many flowers one only is left, that one, fed by the 
sap intended for the others, becomes so much finer. 
If the late figs, which never ripen, are abstracted, the 
early figs the next year are more numerous and 
larger. If of two unequal branches, the stronger 
is shortened and stopped in its growth, the other 
becomes stronger ; and this is one of the most useful 
facts connected with pruning, because it enables a 
skilful cultivator to equalise the rate of growth of all 
parts of a tree ; and as has been already stated, this is 
of the greatest consequence in the operation of bud- 
ding. In fact, the utility of the practice, so common 



244 APPLICATION OF PRINCIPLES. 

in the management of fruit trees which are very 
young, turns entirely upon this. A seedling tree has a 
hundred buds to support, and consequently the stem 
grows slowly, and the plant becomes bushy -headed : 
but being cut down so as to leave only two or three 
buds, they spring upwards with great vigour, and, 
being reduced eventually to one, as happens practi- 
cally, that one receives all the sap, which would other- 
wise be diverted into a hundred buds, and thrives 
accordingly, the bushy head being no longer found, 
but a clean straight stem instead. In the Oak and 
the Spanish Chesnut this is particularly conspicuous. 
Nothing is more strictly to be guarded against than 
the disposition to bleed, which occurs in some plants 
when pruned, and to such an extent as to threaten 
them with death. In the Vine, in milky plants, and 
in most climbers or twiners, this is particularly con- 
spicuous ; and it is not unfrequently observed in 
fruit trees with gummy or mucilaginous secretions, 
such as the Plum, the Peach, and other stone fruits. 
This property usually arises from the large size of the 
vessels through which sap is propelled at the periods 
of early growth, which vessels are unable, when cut 
through, to collapse sufficiently to close their own 
apertures, when they necessarily pour forth their 
fluid contents as long as the roots continue to absorb 
them from the soil. If this is allowed to continue, 
the system becomes so exhausted as to be unable to 
recover from the shock, and the plant will either 
become very unhealthy, or will die.* The only 

* [A solution of Gum Shellac in alcohol, of the consistence of thin 



OF PRUNING. 245 

mode of avoiding it is to take care never to wound 
such trees at the time when their sap first, begins 
to flow ; after a time, the demand upon the system 
by the leaves becomes so great that there is no sur- 
plus, and therefore bleeding does not take place when 
a wound is inflicted.* 

All these things show how extremely necessary it 
is to perform the operations of pruning with care and 
discretion. But, in addition to the general facts 
already mentioned, there are others of a more special 
kind that require attention. The first thing to be 
thought of is the peculiar nature of the plant under 
operation, and the manner in which its special habits 
may render a special mode of pruning necessary. For 
example, the fruit of the Fig and. Walnut is borne by 
the wood of the same season ; that of the Yine and 
Filbert by that of the second season ; and Pears, 
Apples, &c, by wood of some years' growth ; it is 

paste (put on with a brush,) is an admirable application to -wounds 
of stone-fruit trees, and others, which are disposed to bleed pro- 
fusely. It is readily applied, adheres closely, excludes the air com- 
pletely, and is less offensive to the eye than large plasters of clay, 
composition, <fce. A. J. D.] 

* " The Vine often bleeds excessively when pruned in an impro- 
per season, or when accidentally wounded; and, I believe, no mode 
of stopping the flow of the sap is at present known to gardeners. I 
therefore mention the following, which I discovered many years ago, 
and have always practised with success :- — If to four parts of scraped 
cheese be added one part of calcined oyster shells, or other pure cal- 
careous earth, and this composition be pressed strongly into the 
pores of the wood, the sap will instantly cease to flow ; so that the 
largest branch may, of course, be taken off at any season with 
safety." {Knight in Hart. Trans., I 102.) 



246 APPLICATION OF PRINCIPLES. 

clear that plants of these three kinds will each require 
a distinct plan of pruning for fruit. 

The pruner has frequently no other object in view 
than that of thinning the branches so as to allow the 
free access of light and air to the fruit ; and if this 
purpose is wisely followed, by merely removing super- 
fluous foliage, the end attained is highly useful ; it is 
clear, however, that in order to arrive at this end, 
without committing injury to the tree which is operat- 
ed on, it is indispensable that its exact mode of bear- 
ing fruit should be in the first instance clearly ascer- 
tained. 

The period of ripening fruit is sometimes changed 
by skilful pruning, as in the case of the Kaspberry, 
which may be made to bear a second crop of fruit in 
the autumn, after the first crop has been gathered. 
In order to effect this, the strongest canes, which 
in the ordinary course of things would bear a quan- 
tity of fruiting twigs, are cut down to within two or 
three eyes of the base ; the laterals thus produced, 
being impelled into rapid growth by an exuberance 
of sap, are unable to form their fruit buds so early as 
those twigs in which excessive growth is not thus 
produced; and, consequently, while the latter fruit 
at one season, the others cannot reach a bearing state 
till some weeks later. Autumnal crops of summer 
roses, and of strawberries, have been sometimes pro- 
cured by the destruction of the usual crop at a very 
early period of the season ; the sap intended to 
nourish the flower buds destroyed is, after their 
removal, expended in forming new flower buds, 



OF PRUNING. 



247 



which make their appearance at a later part of the 
year. 

The season for pruning is usually midwinter, or at 
midsummer ; the latter for the purpose of removing 
new superfluous branches, the former for thinning and 
arranging the several parts of a tree. It is, however, 
the practice, occasionally, to perform what is called 
the winter pruning early in the autumn, as in the case 
of the Gooseberry^ and of the Vine when weak ; and 
the effect is found to be, that the shoots of such plants, 
in the succeeding season, are stronger than they would 
have been had the pruning been performed at a much 
later season. This is necessarily so, as a little reflec- 
tion will show. During the season of rest (winter) a 
plant continues to absorb food solely from the earth by 
its roots (31) ; and, if its branches 
. are unpruned, the sap thus and then 

e introduced into the system will be 
distributed equally all through it ; let 
us say from b to c d and e in the 
accompanying diagram. If late pru- 
ning is had recourse to, and the 
branches from a to c d and e are re- 
moved, of course a large proportion 
of the sap that has been accumulat- 
ing during the winter will be thrown 
\ away, and b to c will retain no more 

I of it than the exact proportion which 

that part bears to the part abstracted. 
When, however, early or autumnal pruning is employ- 
ed, a to c d and e are removed before the sap has 




248 APPLICATION OF PRINCIPLES. 

accumulated in them, and then all which the roots are 
capable of collecting during the period of repose will 
be deposited in the space from b to a, and conse- 
quently branches from that part will necessarily 
push with excessive vigour. As, however, pruning 
is by no means intended at all times to increase the 
vigour of a plant, late or spring pruning, if not de- 
ferred till the sap is in rapid motion, may be the more 
judicious. 

With regard to pruning plants when transplanted, 
there can be no doubt that it is more frequently inju- 
rious than beneficial. It is supposed, or seems to be, 
that when the branches of a transplanted tree are 
headed back, the remaining buds will break with 
more force than if the pruning had not been perform- 
ed ; but it is to be remembered that a transplanted 
tree is not in the state supposed in the case put at 
page 235, fig. 31. Its roots are not fully in action, 
but from the injuries sustained in removing they are 
capable of exercising but little influence on the 
branches. The great point to attain, in the first in- 
stance, is the renovation of the roots, and that will 
happen only in proportion to the healthy action of the 
leaves and buds (31): if, therefore, the branches of a 
plant are removed by the pruning knife, a great ob- 
stacle is opposed to this renovation j but, if they re • 
main, new roots will be formed in proportion to their 
healthy action. The danger to be feared is, that the 
perspiration of the leaves may be so great as to ex- 
haust the system of its fluid contents faster than the 
roots can restore them, and in careless transplanting 



OF PRUNING. 249 

this may doubtless happen : in such cases it is cer- 
tainly requisite that some part of the branches should 
be pruned away ; but no more should be taken off 
than the exigency of the case obviously requires : 
and, if the operation of transplanting has been well 
performed, there will be no necessity whatever. In 
the case of the transplantation of large trees, it is al- 
leged that branches must be removed, in order to re- 
duce the head, so that it may not be acted upon by 
the wind ; but in general it is easy to prevent this ac- 
tion by artificial means.* 

* The first impulse of every young planter is to leave the entire 
head of a transplanted tree untouched ; and we fear such novices will 
find too abundant authority for this exercise of their sympathies in 
the foregoing paragraph. But sound as the advice is, for a damp 
climate, we are forced by experience to adopt the continental mode 
in this country, and reduce the heads of all trees, more or less, on 
transplanting them. The demand upon the roots in our dry sum- 
mers, especially the first season after removal, is usually much greater 
than they can supply, and we have seen numberless cases where 
they have put out a fine show of green leaves and commenced a 
tolerable growth at first, only to wither and die in mid-summer ; 
while others, treated precisely like them in all other respects, except 
that their branches were shortened back, grew freshly and luxuri- 
antly all the season. Certainly nothing appears more foolish and 
unnecessary than to wantonly spoil the fair proportions of a young 
tree whose branches have begun to assume something of graceful 
symmetry : but when the experience of all old planters conclusively 
proves that transplanted trees whose heads have been shortened 
back somewhat at the extremity of every branch, have succeeded 
almost without exception, and have always grown more vigorously, 
and, in a few seasons, have always regained more beautiful heads 
than those left untouched by the knife, the novice must be 
stubborn who will plant his tree, in this climate, and see it fail 
because he will not reduce the top sufficiently to restore the balance 
of action between the roots and the leaves. A. J. D. 



250 APPLICATION OF PRINCIPLES. 

In the nurseries it is a universal practice to prune 
the roots of transplanted trees ; in gardens, this is as 
seldom performed. Which is right? If a wounded 
or bruised root is allowed to remain upon a trans- 
planted tree, it is apt to decay, and this disease may 
spread to neighbouring parts, which would otherwise 
be healthy ; to remove the wounded parts of roots is 
therefore desirable. But the case is different with 
healthy roots. We must remember that every healthy 
and unmutilated root which is removed is a loss of 
nutriment to the plant, and that too at a time when 
it is least able to spare it ; and there cannot be any 
advantage in the removal. The nursery practice is 
probably intended to render the operation of trans- 
planting large numbers of plants less troublesome ; 
and, as it is chiefly applied to seedlings and young 
plants with a superabundance of roots, the loss in 
their case is not so much felt. If performed at all, 
it should take place in the autumn, for at that time 
the roots, like the other parts of the plants, are com- 
paratively empty of fluid ; but, if deferred till the 
spring, then the roots are all distended with fluid, 
which has been collecting in them during winter, 
and every part taken away carries with it a portion 
of that nurture which the plant had been laying up 
as the store upon which to commence its renewed 
growth. 

It must now be obvious that, although root-pruning 
may be prejudicial in transplanting trees, it may be 
of the greatest service to such established trees as are 
too prone to produce branches and leaves, instead of 



OF PRUNING. 251 

flowers and fruit In these cases the excessive vigour 
is at once stopped by removal of some of the stronger 
roots, and consequently of a part of the superfluous 
food to which their ** rankness" is owing. The opera- 
tion has been successfully performed on the wall trees 
at Oulton, by Mr, Errington, one of our best English 
gardeners, and by many others, and, I believe, has 
never proved an objectionable practice under judi- 
cious management Its effect is, pro tanto, to cut off 
the supply o£ food, and thus to arrest the rapid 
growth of the branches 5 and the connexion between 
this and the production of fruit has already been ex- 
plained (85), It is bj pushing the root-pruning to 
excess that the Chinese obtain the curious dwarf trees 
which excite so much curiosity in Europe. Mr. 
Livingston's account of their practice is so instructive, 
and contains so much that an intelligent gardener 
may turn to account, that I think it worth repeating 
here, 

" When the dwarfing process is intended, the 
branch which had pushed radicles into the surround- 
ing composition in sufficient abundance, and for a 
sufficient length of time, is separated from the tree, 
and planted in a shallow earthenware flower-pot, of 
an oblong square shape ; it is sometimes made to rest 
upon a flat stone. The pot is then filled with small 
pieces of alluvial clay, which, in the neighbourhood 
of Canton, is broken into bits, of about the size of 
common beans, being just sufficient to supply the 
scanty nourishment which the particular nature of the 
tree and the process require. In addition to a careful 



252 APPLICATION OF PKLXCIPLES. 

regulation of the quantity and quality of the earth, 
the quantity of water, and the management of the 
plants with respect to sun and shade, recourse is had 
to a great variety of mechanical contrivances, to pro- 
duce the desired shape. The containing flower-pot 
is so narrow, that the roots pushing out towards the 
sides are pretty effectually cramped. No radicle can 
descend ; consequently it is only those which run to- 
wards the sides or upwards that can serve to convey 
nourishment properly, and it is easy to regulate those 
by cutting, burning, &c, so as to cramp the growth 
at pleasure. Every succeeding formation of leaves 
becomes more and more stunted, — the buds and 
radicles become diminished in the same proportion, — 
till at length that balance between roots and leaves 
is obtained which suits the character of the dwarf re- 
quired. In some trees this is accomplished in two or 
three years, but in others it requires at least twenty 
years." (HorL Trans., iv. 229.) 

We have still to consider that peculiar kind of pru- 
ning which is technically called ringing (Jig. 32.) 
This consists in removing from a branch one or more 
rings of bark, by which the return of sap from the 
extremities is obstructed, and it is compelled to accu- 
mulate above the ring. Mr. Knight explains the 
physiological nature of the operation so well, that I 
cannot do better than quote his words. 

" The true sap of trees is wholly generated in their 
leaves, from which it descends through their bark to 
the extremities of their roots, depositing in its course 
the matter which is successively added to the tree ; 



OF PRUNING. 



253 



whilst whatever portion of such 
sap is not thus expended sinks 
) into the alburnum, and joins the 
ascending current, to which it 
communicates powers not pos- 
sessed by the recently absorbed 
fluid. When the course of the 
descending current is intercept- 
ed, that naturally stagnates and 
accumulates above the decorti- 
cated space; whence it is re- 
pulsed and carried upwards, to 
be expended in an increased 
production of blossoms, and of 
fruit : and, consistently with 
these conclusions, I have found 
that part of the alburnum which 
is situated above the decorticat- 
ed space to exceed in specific 
> gravity, very considerably, that 
which lies below it. The re- 
pulsion of the descending fluid, 
therefore, accounts, I conceive, 
satisfactorily, for the increased 
production of blossoms, and 
more rapid growth of the fruit 
upon the decorticated branch : but there are causes 
which operate in promoting its more early maturity. 
The part of the branch which is below the decorti- 
cated space is ill supplied with nutriment, and ceases 
almost to grow; it in consequence operates less ac- 




254 APPLICATION OF PRINCIPLES. 

tivelj in impelling the ascending current of sap, 
which must also be impeded in its progress through 
the decorticated space. The parts which are above it 
must, therefore, be less abundantly supplied with 
moisture ; and drought, in such cases, always operates 
very powerfully in accelerating maturity. When 
the branch is small, or the space from which the bark 
has been taken off is considerable, it almost always 
operates in excess ; a morbid state of early maturity 
is induced, and the fruit is worthless. 

" If this view of the effects of partial decortication, 
or ringing, be a just one, it follows that much of the 
success of the operation must be dependent upon the 
selection of proper seasons, and upon the mode of 
performing it being well adapted to the object of the 
operator. If that be the production of blossoms, or 
the means of making the blossoms set more freely, 
the ring of bark should be taken off early in the sum- 
mer preceding the period at which blossoms are re- 
quired : but, if the enlargement and more early ma- 
turity of the fruit be the objects, the operation should 
be delayed till the bark will readily part from the 
alburnum in the spring. The breadth of the decorti- 
cated space must be adapted to the size of the branch ; 
but I have never witnessed any except injurious 
effects, whenever the experiment has been made upon 
very small or very young branches, for such become 
debilitated and sickly, long before the fruit can ac- 
quire a proper state of maturity." 

The effects of ringing in altering the appearance of 
the fruit is very striking. In the Horticultural Tnuis- 



OF PRUNING. 255 

actions, iii. 367, the following cases are reported. — In 
a French Crab, the fruit, by ringing, was increased to 
more than double the size, and the colour of it was 
much brightened. In a Minshull Crab the size was 
not increased, but the appearance of the apple was so 
improved as to make it truly beautiful ; its colours, 
both red and yellow, were very bright. In the Court- 
pendu Apple the improvement was still more conspi- 
cuous, the colours being changed from green and dull 
red, to brilliant yellow and scarlet. Many others of a 
similar kind are to be found recorded in books on hor- 
ticulture. It is, however, by no means alone to the 
maturation or production of fruit that this operation 
is applicable ; it will, of course, induce also the pro- 
duction of flowers, and it has occasionally been used 
for that purpose, as in the Camellia. It is best per- 
formed in the early spring, when the bark first sepa- 
rates freely from the wood. 

This operation has, however, the disadvantage of 
wounding a branch severely ; and, if performed ex- 
tensively upon a tree, it is very apt, if not to kill it, 
at least to render it incurably unhealthy ; for if the 
rings are not sufficiently wide to cut off all communi- 
cation between the upper and lower lips of the wound 
they produce little effect, and if they are, they are 
difficult to heal. For these reasons the operation is 
but little employed, other means being used instead. 
By some persons ligatures are made use of, and they 
would be preferable if they answered the purpose of 
obstructing the sap to the same extent as the abstrac- 
tion of a ring of bark. In Malta, one of the objects 



256 APPLICATION OF PRINCIPLES. 

of ringing, that of advancing the maturation of the 
fruit, is practised upon the Zinzibey, or Jujube tree, by 
merely fixing in the fork of a branch a very heavy 
stone, made fast with bandages ; its weight forces the 
branches a little into a horizontal direction, and thus, 
independently of the pressure it exercises upon the 
parts it touches, obstructs the free circulation of the 
sap. 



CHAPTER XIV. 
OF TRAINING. 

Training is one of the most artificial operations 
that gardeners are acquainted with, its object being to 
place a plant in a condition to which it could never 
arrive under ordinary circumstances. The practice 
of it forms one of the most complicated parts of the 
art of horticulture, each species demanding a method 
peculiar to itself; but the principles on which it 
depends are few and simple. These will be best con- 
sidered with reference to the objects the gardener 
wishes to attain in performing the operation. 

It is probable that the intention of the first gar- 
dener who trained a tree was to gain some advantage 
of climate, by placing the tree close to a wall or other 
screen ; and this is still one of the greatest objects ; 
partly with a view to guard the flowers in spring 
from cold, and especially cold winds, partly to expose 



OF TRAINING. 257 

the leaves and fruit to a hotter temperature than 
would otherwise be gained, and in some measure to 
ripen wood with more certainty. 

That training a tree over the face of a wall will 
protect the blossoms from cold must be apparent, 
when we consider the severe effect of excessive eva- 
poration upon the tender parts ; a merely low tempe- 
rature will produce but little comparative injury in a 
still air, because the more essential parts of the flower 
are very much guarded by the bracts, calyx, and 
petals, which overlie them, and, moreover, because 
radiation (see page 136) will be intercepted by the 
branches themselves placed one above the other, so 
that none but the uppermost branches which radiate 
into space will feel its full effects ; but, when a cold 
wind is constantly passing through the branches and 
among the flowers, the perspiration, against which no 
sufficient guard is provided by nature, becomes so 
rapid (see page 129) as to increase the amount of cold 
considerably, besides abstracting more aqueous mat- 
ter than a. plant can safely part with. This being one 
of the great objects of training trees, it is inconceiv- 
able how any one should have recommended such 
devices as those mentioned in the Horticultural Trans- 
actions, ii. Appendix, p. 8, of training trees upon a 
horizontal plane ; the only effect of which would be 
to expose a tree as much as possible to the effect 
of that radiation which it is the very purpose of train- 
ing to guard against. 

The actual temperature to which a tree trained 
upon a wall facing the sun is exposed is much higher 



258 APPLICATION OF PRINCIPLES. 

than that of the surrounding air, not only because it 
receives a larger amount of the direct solar rays, but 
because of the heat received by the surrounding earth, 
reflected from it and absorbed by the wall itself. 
Under such circumstances the secretions of the plant 
are more fully elaborated than in a more shady and 
colder situation ; and, by aid of the greater heat and 
dryness in front of a south wall, the period of matu- 
rity is much advanced. In this way we succeed 
in procuring a Mediterranean or Persian summer 
in these northern latitudes. When the excellence of 
fruit depends upon its sweetness, the quality is ex- 
ceedingly improved by such an exposure to the sun ; 
for it is found that the quantity of sugar elaborated 
in a fruit is obtained by an alteration of the gummy, 
mucilaginous, and gelatinous matters previously 
formed in it, and the quantity of those matters will 
be in proportion to the amount of light to which the 
tree, if healthy, has been exposed. Hence the greater 
sweetness of plums, pears, &c, raised on walls from 
those grown on standards. It has been already 
stated (page 138) that an increase of heat has been 
sought for on walls by blackening them ; and we are 
assured in the Horticultural Transactions (iii. 330) that, 
in the cultivation of the Grape, this has been attended 
with the best effects. But, unless when trees are 
young, the wall ought to be covered with foliage dur- 
ing summer, and the blackened surface would scarcely 
act ; and in the spring the expansion of the flowers 
would be hastened by it, which is no advantage in 
cold late springs, because of the greater liability of 



OF TBAINING. 259 

earl j flowers to perish from cold. That a blackened 
surface does produce a beneficial effect upon trees 
trained oyer it, is, however, probable, although not in 
insuring the maturation of fruit ; it is by raising 
the temperature of the wall in autumn when the 
leaves are falling, and the darkened surface becomes 
uncovered, that the advantages are perceived by a 
better completion of the process of growth, the result 
of which is ripening the wood. This is, indeed, the 
view taken of it by Mr. Harrison, who found the 
practice necessary, in order to obtain crops of pears 
in late seasons at Wortley in Yorkshire (see HorL 
Trans. , iii. 330, and vi. 453.) It hardly need be 
added that the effect of blackening will be in propor- 
tion to the thinness of the training, and vice versa. 

Another object of training is, to place a tree in such 
a state of constraint that its juices are unable to cir- 
culate freely, the result of which is exactly that 
already assigned to the process of ringing (see p. 
254). If a stem is trained erect, it will be more 
vigorous than if placed in any other position, and its 
tendency to bear leaves rather than flowers will be 
increased ; in proportion as it deviates from the per- 
pendicular is its vigour diminished. For instance, if 
a stem is headed back, and only two opposite buds 
are allowed to grow, they will continue to push 
equally, so long as their relation to the perpendicular 
is the same ; but, if one is bent towards a horizontal 
direction, and the other allowed to remain, the growth 
of the former will be immediately checked ; if the 
depression is increased, the weakness of the branch 



260 APPLICATION OF PRINCIPLES. 

increases proportionally ; and this may be carried on 
till the branch perishes. In training, this fact is of 
the utmost value in enabling the gardener to regu- 
late the symmetry of a tree. It however by no 
means follows that, because of two continuous 
branches, one growing erect and the other forced 
into a downward direction, the latter may die, that all 
branches trained downwards will die. On the con- 
trary, an inversion of their natural position is of so 
little consequence to their healthiness, that no effect 
seems in general to be produced beyond that of 
causing a slow circulation, and the formation of 
flowers. Hence the directing of branches downwards 
is one of the commonest and most successful contri- 
vances employed by gardeners to render plants fruit- 
ful. Mr. Knight was the first to recommend the 
practice in the following account of his recovery of 
an old and worthless Pear tree : 

11 An old St. Germain Pear tree, of the spurious 
kind, had been trained in the fan form, against a 
north-west Avail in my garden, and the central 
branches, as usually happens in old trees thus train- 
ed, had long reached the top of the wall, and had be- 
come wholly unproductive. The other branches 
afforded but very little fruit, and that never acquiring 
maturity was consequently of no value ; so that it 
was necessary to change the variety, as well as to 
render the tree productive. To attain these purposes, 
every branch which did not want at least twenty de- 
grees of being perpendicular was taken out at its 
base ; and the spurs upon every other branch, which 



OF TKAINING. 261 

I intended to retain, were taken off closely with the 
saw and chisel. Into these branches, at their sub- 
divisions, grafts were inserted at different distances 
from the root, and some so near the extremities of the 
branches, that the tree extended as widely in the au- 
tumn after it was grafted, as it did in the preceding 
3^ear. The grafts were also so disposed, that every 
part of the space the tree previously covered was 
equally well supplied with young wood. 

" As soon, in the succeeding summer, as the young 
shoots had attained sufficient length, they were train- 
ed almost perpendicularly downwards, between the 
larger branches and the wall, to which they were 
nailed. The most perpendicular remaining branch 
upon each side was grafted about four feet below the 
top of the wall, which is twelve feet high ; and the 
young shoots, which the grafts upon these afforded, 
were trained inwards, and bent down to occupy the 
space from which the old central branches had been 
taken away; and therefore very little vacant space 
remained any where in the end of the first autumn. 
A few blossoms, but not any fruit, were produced by 
several of the grafts in the succeeding spring; but in 
the following year, and subsequently, I have had 
abundant crops, equally dispersed over every part of 
the tree ; and I have scarcely ever seen such an ex- 
uberance of blossom as this tree presents in the pre- 
sent spring." (Rort. Trans., ii. 78.) 

The practice was then followed by Sir Joseph 
Banks, whose fruit trees, trained downwards over the 
walls of his garden at Spring Grove, and facing the 



262 



APPLICATION OF PRINCIPLES. 



high road, long excited the astonishment of passers- 
by ; and it has now been generally applied to other 
cases. What are called Balloon Apples and Pears, 
formed by forcing downwards all the branches of 
standard trees till the points touch the earth, are an 
instance of this ; and they have the merit of produc- 
ing large crops of fruit in a very small compass : their 
upper parts are, however, too much exposed to ra- 
diation at night, and the crop from that part of the 
branches is apt to be cut off. One of the prettiest 
applications of this principle is that of Mr. Charles 
Lawrence, described in the Gardener s Magazine, viii. 




OF TRAINING. 263 

680, by means of which standard Eose trees are con- 
verted into masses of flowers. The figure given in 
that work, and here reproduced {fig. 33), represents 
the variety called the Bizarre de la Chine, " which 
flowered most abundantly to the ends of its branches, 
and was truly a splendid object." 

The last object of training to which it is necessary 
to advert is that of improving the quality of fruit, by 
compelling the sap to travel to a very considerable dis- 
tance. The earliest notice of this, with which I am 
acquainted, is the following by Mr. Williams of 
Pitmaston. 

" Within a few years past," he says in 1818, " I 
have gradually trained bearing branches of a small 
Black Cluster Grape, to the distance of near fifty feet 
from the root, and I find the branches every year 
grow larger, and ripen earlier as the shoots continue 
to advance. According to Mr. Knight's theory of 
the circulation of the sap, the ascending sap must 
necessarily become enriched by the nutritious par- 
ticles it meets with in its progress through the stems of 
the alburnum ; the wood at the top of tall trees, there- 
fore, becomes short-jointed and full of blossom buds, 
and the fruit there situated attains its greatest perfec- 
tion. Hence we find Pine and Fir trees loaded with 
the finest cones on the top boughs ; the largest acorns 
grow on the terminal branches of the Oak, and the 
finest mast on the high boughs of the Beech and Chest- 
nut ; so likewise apples, pears, cherries, &c, are al- 
ways best flavoured from the top of the tree." {Hort. 
Trans., iii. 250, 251.) The merit of the Fontainbleau 



264 



APPLICATION OF PRINCIPLES. 



mode of training the Vine (fig. 34), in which many 
of the stems are carried to very considerable distances, 
seems to depend in some measure upon this principle ; 




and there is a well-known Black Hamburg Grape at 
Bath, growing in a garden formerly belonging to Mr. 
Farrant, the stem of which, owing to local circum- 
stances, is necessarily conveyed to a very considera- 
ble distance before it is allowed to produce its bearing 
branches, the quality of whose fruit is of very un- 
usual excellence. These facts seem capable of being 
applied to many important improvements in fruit ma- 
nagement. 



OF TRAINING. 265 

The foregoing are the principal advantages which, 
arise from training plants ; let us next consider what 
disadvantages there may be. The only trees which 
at all approach in nature the state of trained plants are 
climbers and creepers, whose stems, unable to support 
themselves, cling for a prop upon whatever they are 
near ; some of them enclose the stem of another plant 
in their convolutions ; others simply attach themselves 
by means of tendrils as the Vine, by hooks as the 
Combretum, or by other contrivances ; and some, 
like the Ivy, lay hold of walls, rocks, or the trunks 
of trees, by their fciinute roots. To none of these 
can that motion be necessary to which plants are 
naturally exposed, and which, as has been already 
seen (p. 157), is of so much importance to the healthy 
maintenance of their functions. Hence it is, that 
among fruit trees the Vine never suffers from being 
trained : indeed its anatomical structure is especially 
suited to such a mode of existence ; while all erect 
trees, of whatever kind, whose branches nature 
intended to be rocked by the storm, and perpetually 
waved by the currents of air to which they are 
exposed, in all cases suffer more or less. 

One of the commonest and worst diseases induced 
by training is a gradual impermeability of tissue 
to the free passage of sap, which appears to stagnate, 
so that in time the branches become debilitated and 
juiceless ; the obstruction to the flow of the sap 
tends to produce coarse shoots from various parts of 
the branches, and especially from the roots. The 
cause of this seems to be the too rapid deposit 
12 



266 APPLICATION OF PRINCIPLES. 

of the sedimentary matter of lignification,* and to 
be induced by want of motion and excessive expo- 
sure of the leaves and branches to the sun. The effect 
of the latter is to inspissate all the juices, and to pro- 
mote their formation ; while the former increases the 
evil by not keeping the fluids in rapid circulation : 
just as we know that a slow stream, from a muddy 
source, deposites its impurities much more copiously 
than a rapid stream. As this evil arises out of the 
operation of training, and seems to be inseparable 
from it, there will be no expectation of a remedy 
being discovered. 

The increase of the saccharine quality of fruit is by 
no means an advantage in all cases ; it improves the 
peach, the nectarine, the pear and the plum, in which 
sweetness is the great object ; but it deteriorates the 
apple and the apricot, which are chiefly valued for 
their peculiar mixture of acidity and sweetness. 

The protection received in the spring by trees 
trained upon walls exposed to the sun, while it 
advances the period of flowering, at the same time 
causes it to take place at a season when they are not 
sufficiently secure from spring frosts ; and hence the 
necessity of protecting such plants artificially by 
coping, screens, bushes, curtains, and other contri- 
vances. It is on this account that the utility of flued 
walls is so much diminished, and that they are found, 
in practice, more valuable for ripening wood in 
autumn, than for guarding blossoms in the spring. 

* See Introduction to Botany, ed. 8, p. 3 



OF POTTING. 267 

CHAPTER XY. 
OF POTTING. 

When a plant is placed to grow in a small earthen 
vessel like a garden pot, its condition is exceedingly 
different from that to which it would be naturally 
exposed. The roots, instead of having the power 
of spreading constantly outwards, and away from their 
original starting point, are constrained to grow back 
upon themselves ; the supply of food is comparatively 
uncertain ; and they are usually exposed to fluctua- 
tions of temperature and moisture unknown in a 
natural condition. For these reasons, potted plants 
are seldom in such health as those growing freely 
in the ground ; but, as the operation of potting is one 
of indispensable necessity, it is for the scientific gar- 
dener, firstly, to guard against the injuries sustainable 
by plants to which the operation must be applied ; 
and, secondly, to avoid, as far as may be possible, 
exposing them to such an artificial state of existence. 
That the latter may be done more frequently than is 
supposed will be sufficiently obvious, when we have 
considered what the purposes really are that the gar- 
dener needs to gain by potting. 

The first and greatest end attained by potting is, 
the power of moving plants about from place to place 
without injury ; greenhouse plants from the open air 
to the house, and vice versa ; hardy species, difficult 
to transplant, to their final stations in the open ground 



268 APPLICATION OF PRINCIPLES. 

without disturbing their roots ; annuals raised in heat 
to the open borders ; and so on : and, when this 
power of moving plants is wanted, pots afford the 
only means of doing so. It also cramps the roots, 
diminishes the tendency to form leaves, and increases 
the disposition to flower. Another object is. to effect 
a secure and constant drainage from roots of water ; 
a third is, to expose the roots to the most favourable 
amount of bottom heat, which cannot be readily 
accomplished when plants of large size are made to 
grow in the ground even of a hot-house ; and, finally, 
it is a convenient process for the nourishment of deli- 
cate seedlings. Unless some one of these ends is to 
be answered, and cannot be effected in a more natu- 
ral manner, potting is better dispensed with. 

That it may be advantageously dispensed with, in 
many cases, is evident from several facts more or less 
well known. The nurserymen prefer " pricking out'' 
their delicate seedlings into pans, or movable bor- 
ders, instead of pots ; and they always thrive the bet- 
ter. In conservatories, the necessity of shifting plants 
from place to place may be often avoided ; while, 
under judicious management, those which are planted 
in the open soil have greatly the advantage of others, 
both in healthiness and easiness of management ; and 
there is no doubt that Pine-apples will succeed better 
unpotted, if planted freely in soil exposed to a proper 
amount of bottom heat. This was first asserted by Mr. 
Martin Call, one of the Emperor's gardeners at St. 
Petersburgh (Hort. Trans., iv. 471), and has been since 
practised very successfully by others. In the year 



OF POTTING. 269 

1830, a pine-apple, obtained by this treatment, weigh- 
ing 91b. 4oz., was sent to the King of England by Mr. 
Edwards of Rheola ; and the success of other growers, 
in the same manner, has been remarkable. (See Hort. 
Trans., n. s., i. 388.) 

The exhaustion of soil by a plant is one of the most 
obvious inconveniences of potting. The organisable 
matter in a soluble state, contained in a garden pot, 
must necessarily be soon consumed by the numerous 
roots crowded into a narrow compass, and continually 
feeding upon it. The effects of this are seen in the 
smallness of leaves, the weakness of branches, the 
fewness and imperfect condition of flowers, &c. ; and 
the gardener remedies them by applying liquid ma- 
nure, by frequent shifting, or by placing his plants in 
pan-feeders, shallow earthen vessels containing ma- 
nure, to which the roots have access through the 
holes in the bottom of a pot. It is, however, to shift- 
ing, more particularly, that recourse is had for reno- 
vating the soil ; and this, if skilfully performed, with- 
out giving a sudden and violent shock to the plant, 
is probably the best means; because the roots are 
thus allowed more liberty of distribution, and the 
earth is kept more open (more permeable) than when 
consolidated by repeated applications of liquid ma- 
nure. There is, however, a difficulty in shifting 
plants without injury to their roots, in the midst of 
full vegetation ; and at such times the application of 
liquid manure is preferable, when the soil requires 
renovation. 

It is not, however, by mere exhaustion that potted 



270 APPLICATION OF PRINCIPLES. 

plants render the soil unfit for their support. Every- 
one knows that the soil of a farm will not bear, year 
after year, the same kind of crop, but that one kind 
of produce is cultivated on a piece of ground one 
year, and is succeeded by some other kind ; which 
practice, in part, constitutes the important system of 
rotation of crops. Not, however, to refer to matters 
extra-horticultural, it is notorious that an apple 
orchard will not immediately succeed upon the site 
of an old orchard of the same kind of fruit, and that 
no amount of manuring will enable it to succeed ; a 
wall border, in which fruit trees have been long 
grown, becomes at last insensible to manure, and re- 
quires to be renewed ; and, not to dwell upon an un- 
disputed fact, Dahlias do not " like" the soil in which 
Dahlias were grown the previous year. This class 
of phenomena cannot be explained upon the principle 
of soil being exhausted, because that exhaustion is 
. made good and yet to no purpose, unless we assume 
that land contains something mineral which each 
species prefers to feed on, and which is not contained 
in manure. But the slender power of selection pos- 
sessed by the roots of plants (35) would be unfavour- 
able to this supposition, even if it were open to no 
other objections. It has of late years been thought 
that the excretory functions of the root (39) would 
explain the deterioration of soil, and that the reason 
why plants cannot grow year after year in the same 
soil, if it and their roots are disturbed, is, that, under 
such circumstances, they are perpetually brought into 
contact with the matter of which nature had previous- 



OF POTTING. 271 

ly relieved them ; this matter being assumed to be 
unsuitable to themselves, although harmless to differ- 
ent species. The subject has been hitherto so little 
investigated that it is not safe, perhaps, to take it as 
the basis of a theory ; but it certainly appears to offer 
a more probable explanation of the deterioration of 
soil than any other yet proposed. There are those, 
indeed, who seem willing to deny altogether that soil 
is deteriorated ; and cases are adduced of Peach trees 
not repotted for twenty years, which did not die ; of 
Strawberry beds not renewed for a long series of 
years, which still bore fruit : but I do not know that 
any one ever asserted that trees would perish if re- 
planted in their own deteriorated soil; it has only 
been said that they would become unhealthy and un- 
productive, and I think few gardeners will deny that. 
Neither has it been pretended that the root-secretions 
of every plant are deleterious at all. It is quite con- 
ceivable that one plant may secrete a deleterious mat- 
ter that is very slowly decomposable, but which may, 
nevertheless, be soluble enough to enter into the food 
of other roots ; and in such a case an injurious effect 
may be produced : while, in another case, the secreted 
matter may be rapidly decomposable, when it will 
enter into new combinations, and lose whatever dele- 
terious property it originally possessed, if any. At 
all events, be the theory what it may, it is an un- 
doubted fact that soil is deteriorated by a plant 
which has grown in it for a long time ; and that, to 
be maintained in a healthy condition, that soil must 
be changed. This explains why potted plants, care- 



272 APPLICATION OF PRINCIPLES. 

fully attended to and often shifted, are so much more 
healthy than those treated otherwise. It is not, how- 
ever, merely for the purpose of removing deterio- 
rated earth or adding manure, that shifting is impor- 
tant ; all potted plants have, in time, their ball of 
earth, by the continual passage of water through it, 
reduced to a state of hardness and solidity unfavour- 
able to the retention of moisture or the growth of 
roots ; and this is of course cured, if the operation of 
shifting is judiciously performed. I must, however, 
confess, I have seen gardeners contented with lifting 
a plant, with a hard old matted ball, out of one pot 
into another of a little larger size, shaking some par- 
ticles of fresh earth in between the ball and the side 
of the pot, and pressing the whole down with as much 
force as the thumbs can give. 

It is found that the roots of potted plants invariably 
direct themselves towards the sides of the pot, as must 
indeed necessarily happen in consequence of their dis- 
position to grow horizontally. Having reached the 
sides, they do not turn back, but follow the earthen- 
ware surface, till at last they form an entangled stra- 
tum enclosing a ball of earth ; then, if not relieved 
by repotting, they rise upwards towards the surface, 
or they attempt to force themselves back to the centre. 
The greater part, however, are always found in con- 
tact with the porous earthen side of the vessel ; and 
especially all the most powerfully absorbent, that is, 
youngest parts. They are, therefore, in contact with 
a body subject to great variations of temperature and 
moisture, in consequence of exposure to the sun, or to 



OF POTTING. 273 

a dry air in motion, unless in those rare cases where 
the air is kept by artificial means shaded, and uni- 
formly damp. By these means, in a dry summer day, 
when the leaves are perspiring freely, and therefore 
requiring an abundance of water from the roots, the 
latter are placed in contact with a substance whose 
moisture is continually diminishing ; or in a green- 
house where the pots are syringed, the heat of the 
earth in contact with the roots is lowered by a copious 
evaporation from the sides of the pot, just when, in 
nature, the bottom heat should be the greatest. The 
evil consequences of this are well known to gardeners, 
who however seldom take any sufficient precautions 
to prevent it. Greenhouse plants exposed to the 
open air in summer always suffer severely from the 
irregular condition of the sides of the pots ; whence 
the common practice of .plunging them in the earth, 
for the purpose of bringing them into the condition 
of plants growing in the open ground. 

This is, however, attended with some disadvan- 
tage : for the plants root, through the bottom of the 
pots or over the edges, among the earth in which 
they are plunged ; and, when taken up in the autumn 
for removal into the greenhouse, they must have all 
such roots cut off again ; for there are no means of 
bringing them within the limits of a pot. For these 
and similar reasons, no good gardener will expose his 
greenhouse plants to the open air in summer, if he can 
help it, unless they are duplicates, or unless there is 
some object to be attained very different from the 
strange notion that ihey are hardened by this pro- 
12* 




274 APPLICATION OF PRINCIPLES. 

cess. The effect that is really produced upon them 
is, to give them a sort of artificial winter in summer, 
that is, to expose them to a period of comparative 
rest from growth, which, in many cases, is useful. 
The best method of counteracting the injurious 
effects of exposure to the air is 
) by employing double pots (fig. 
35), as recommended in the 
Gardener's Magazine, ix. 576, 
and by Captain Mangles, in his 
Floral Calendar, p. 44 ; the space 
(b) between the two pots being 
filled up with moss, or any other 
substance retentive of moisture. 
Of course the inconveniences now alluded to are 
principally sustained by plants in small pots: when 
the quantity of earth is considerable, as in tubs or 
the largest kinds of pots, the loss of water through 
the sides is of little moment ; and the variation of 
temperature is more than counteracted by the large 
surface exposed to the direct influence of the solar 
rays. In these cases, the perfect drainage of super- 
fluous moisture is often of the greatest service. Mr. 
Knight, indeed, assures us that " plants of every 
species are more or less affected, but not all inju- 
riously, by having the sides of their pots exposed 
fully to the air. The taste and flavour of the peach 
and nectarine, and still more of the strawberry, are 
greatly improved; and the Fig-tree, in the stove, 
is made to afford a longer succession of produce, 
owing to the succession of young shoots, which are 



OF POTTING. 275 

caused to spring from its larger branches and stems ; 
and, in all cases when trees can be made to retain their 
health in exposed pots, the period of the maturity of 
their fruit is very considerably accelerated. (Hort. 
Trans,, vii. 258.) 

It seems to be nothing but the complete drainage 
to which they are then exposed, that makes the 
Orange and all its tribe, naturally inhabitants of the 
hill-sides of the temperate parts of Asia, thrive 
best when the roots come in contact with the sides of 
the pots, &c., in which they grow. In all cases, the 
drainage should be most carefully secured, by placing 
an abundance of broken tiles, potsherds, &c, in the 
bottom of a pot, so as to prevent the stagnation of 
water (page 119) about the roots. 

Mr. Macnab, in his excellent practical treatise upon 
the cultivation of Cape Heaths, points out very forci- 
bly the value of good draining to that class of plants. 
There is scarcely any danger, he says, of giving too 
much draining; and, in order to effect this essential 
object still more perfectly, he, in shifting his Heaths, 
constantly keeps the centre elevated above the gene- 
ral level of the earth in the pot or tub, so that at 
last each plant stands on the summit of a small hillock. 

In order to counteract the risk of excessive drain- 
age, without in reality diminishing it, great advan- 
tage is derived from the introduction into the earth 
of fragments of some absorbent stone. Mr. Macnab 
uses u coarse soft free-stone, broken into pieces from 
one inch to four or five inches in diameter ;" because 
in summer these stones retain moisture longer than 



276 APPLICATION OF PRINCIPLES. 

the earth, and in winter allow a free circulation of 
any superabundant moisture. 

If woody plants are allowed to remain growing in 
the same pot for many years, as is sometimes the 
case, one of two things must happen ; either the 
roots, matted into a hard ball, become so tortuous 
and hard as to be unfit for the free passage of sap 
through them, or they acquire a spiral direction. In 
either case, if such plants are turned out of their 
pots in a conservatory, or in the open ground, with a 
view to their future growth in a state of liberty, new 
roots will be made with difficulty, and it will be 
a long time before the effects of growth in the free 
soil will be apparent. Where the spiral or corkscrew 
direction has been once taken by the roots, they are 
very apt to retain it during the remainder of their 
lives ; and if, when they have become large trees, 
they are exposed to a gale of wind, they readily 
blow out of the ground, as was continually happen- 
ing with the Pinaster some years ago, when the nur- 
serymen kept that kind of Fir for sale in pots. In 
all such cases as these, the roots should be carefully 
disentangled and straightened at the time when trans- 
plantation takes place. 

If, however, a potted plant is managed in the most 
perfect manner, no such entanglement or coiling up 
will take place. To be managed perfectly, a plant, 
when young, should be placed in as small a pot as it 
will grow in, and it should be gradually and succes- 
sively transferred to larger pots as it advances in 
size. If this is done, the warmth to which the pot 



OF POTTING. 277 

is exposed will be more immediately felt by the roots ; 
the latter, as they grow, will ramify regularly all 
through the mass of earth, which, moreover, will 
be thoroughly drained : but if, on the other hand, a 
very small young plant is placed at once in a large 
pot, and left to grow there, the drainage will be less 
perfect, the large mass of earth will be less sensible 
of the heat to which it is exposed, the roots will from 
the first take a horizontal direction towards the out- 
side of the pot, and, once there, will follow its surface 
as has been already stated, exhausting the small 
quantity of earth with which they are then in con- 
tact, and profiting little or nothing by the main body 
of soil in the interior of the pot. As the proper 
manner of managing potted plants is of the first con- 
sequence, I transcribe the following mode of treating 
the Balsam, from a very sensible paper by the Eev. 
William Williamson. 

" As soon as they have got four leaves, I trans- 
plant them singly into the smallest pots lean procure, 
and in such a manner that the stem of the plant may 
be covered somewhat more than it was at first, and 
then all are to be again placed in the frame. In a 
short time, if there be a sufficiency of heat ; that part 
of the stem which is covered with the mould puts 
forth fibres, by which nourishment is conveyed more 
immediately to the principal stem of the plant. As 
soon as the plants are a little advanced in growth, 
they are again removed (if possible without disturb 
ing the earth) into somewhat larger pots, still plant- 
ing them rather deeper than before. The same process 



278 APPLICATION OF PRINCIPLES. 

is repeated five or six times, till, at last, they are 
removed into their final pots. I have found it best 
to give them their last removal after they have 
opened their first blossoms, as it gives additional 
brilliancy and size to the flowers. By following this 
method the plant acquires extraordinary vigour, 
throwing out its branches from the surface of the 
mould, exhibiting flowers nearly as large as a full- 
blown rose, and a stem measuring two, and some- 
times three, inches in circumference." (Hort. Trans., 
iii. 128). 

The plan of continually sinking the stem with 
every succeeding potting is useful to the Balsam, 
because it puts forth roots in abundance from its 
stem ; and to all plants having the same property, 
the same practice is desirable : but not to others, 
which, if their stems do not root as fast as they 
are buried, will suffer injury by the sinking. 

It is by paying constant attention to the shifting 
of the growing plant, by the employment of a very 
rich stimulating soil, and by a thorough knowledge 
of the kind of atmosphere which suits them best, that 
have been obtained those magnificent Pelargoniums, 
Cockscombs, Balsams, and similar flowers, which 
have so often and so justly excited the admiration of 
even the most experienced gardeners. 



OF TEANSPL ANTING. 279 

CHAPTEE XVI. 
OF TRANSPLANTING. 

As soon as man attempted to beautify his residence 
with trees planted around it, he would naturally 
obtain them from the forest ; and he then would find 
that, of many that he removed, all or some at least 
would die : if however he persevered, he would 
at last discover that while constant failure attended 
his efforts at one time, comparative success would 
crown them at another ; and he would thus be led to 
investigate, according to his skill, the causes of suc- 
cess and failure. Out of this would grow in time the 
art of transplanting, among the most important busi- 
ness of the gardener. 

I fear, however, it is too generally practised as an 
empirical art, without sufficient attention being paid 
to the principles on which its success or failure 
depend ; at least, one hardly knows how to draw any 
other conclusion from the opposite opinions held by 
planters, the dogmatical manner in which they are 
too often expressed, and the obscure and unintelligi- 
ble phraseology of what are called explanations of the 
practice by amateurs, to whom it is not necess -ry to 
allude more particularly. If there is any one part of 
the art of Horticulture in which post hoc has been 
mistaken for propter hoc more commonly than ano- 
ther, it is surely in what concerns transplantation.* 

* It is scarcely necessary to say that these remarks do not, in any 



280 APPLICATION OF PRINCIPLES. 

And yet the rationale is simple enough, if we do not 
labour to render it confused by imaginary refine- 
ments. 

When a plant is taken out of the ground for trans- 
planting, its roots are necessarily more or less injured 
in the process, and consequently it is less able to sup- 
port the stem than it was before the mutilation took 
place ; its loss of this power will also be in proportion 
to the extent of the mutilation, which may be carried 
so far as to amount to destruction. 

But the importance of their roots to plants is not 
alike at all seasons ; in the summer, when there is the 
greatest demand upon them in consequence of the 
perspiration of the foliage (70, &c), they are most 
essential ; in winter, when the leaves have fallen, 
they are comparatively unimportant, as is evident 
from a very common case. Let a limb of a tree be 
felled in full leaf in June ; its foliage will presently 
wither, the bark will shrivel and dry up, and the 
whole will speedily perish ; but, if a similar limb is 
lopped in November, when its foliage has naturally 
fallen off, it will exhibit no sign of death during win- 
ter, nor till the return of spring, when it may make a 
dying effort to recover ; but the means it takes to do 
so, namely, the emission of leaves, only accelerates 
its end. 

These two propositions really include all the most 

way apply to Mr. Macnab's Hints on the Planting and Gtneral 
Treatment of Hardy Evergreens in the Climate of Scotland ; an 
excellent treatise, which it is impossible to recommend too strongly 
to the attention of the planter. 



OF TRANSPLANTING. 281 

essential parts of the theory of transplantation, as 
will presently be seen : it is necessary, however, that 
they should be applied in some detail ; for which pur- 
pose it will be convenient to consider, first, the season, 
and, secondly, the manner, in which transplanting 
can be best effected. 

It is the powerful perspiratory action of the leaves 
of deciduous trees which renders transplanting them 
in a growing state so difficult, that for practical pur- 
poses it may be called impossible ; for the operation 
is necessarily- attended by a mutilation of the roots 
which feed the leaves. At no period, then, can the 
operation be performed if such plants are growing. 
Even if the buds are only pushing, the process should 
be avoided, because immediately after that period 
the demand upon the roots is greatest; for although 
in consequence of the smallness of the surface of the 
young leaves the action of perspiration may seem to 
be feeble, yet the thinness of the newly formed tissue 
will not enable it to resist the drying action of the 
atmosphere unless there is a most abundant afflux of 
sap from the roots. In England, too, the months 
when buds begin to burst forth are objectionable, 
not only on account of their dryness (see the tables 
at page 133), but of their coldness, which prevents 
the free circulation of sap ; and their evil effects are 
felt not only by the roots through the foliage, but 

* Transplanting from garden pots, in which the roots are pre- 
served artificially from injury, may be performed equally well at 
any time if care is taken, and is, of course, not included in this 
statement. 



282 APPLICATION OF PRINCIPLES. 

directly, as will be shown hereafter. The season, 
then, which ought to be chosen is the period that 
intervenes between the fall of the leaf in autumn and 
the earliest part of spring, before the sap begins 
to move and the dry cold winds of that season to pre 
vail. I entirely agree with Mr. Macnab, that the 
earliest time at which planting can be effected is, 
upon the whole, the best ; a conclusion to which he 
has come from his extensive practice, in which my 
own observation of a great deal of planting for the 
last twenty-five years coincides, and which is, in all 
respects, conformable to theory. As soon as a plant 
has shed its leaves, it is as much at rest for the season 
as it will be at any subsequent period, unless it is 
frozen; its torpor, indeed, is greater at that time, 
because its excitability is completely exhausted by 
the season of growth, and it has had no time to reco- 
ver it. If, at that time, a root is wounded, a process 
of granulation or cicatrisation will commence, just as 
it does in cuttings (page 200) ; and from that granu- 
lation, which is a mere developement of the horizon- 
tal cellular system (45), roots will eventually proceed. 
Now, it is obvious that since roots must be wounded 
in the process of transplantation, the sooner the wound 
is made the better, because it has the longer time in 
which to heal ; and therefore the earlier in the autumn 
transplanting is effected, the less injury will be sus- 
tained by the plant submitted to the process ; in the 
technical language of the gardener, " it has the more 
time to establish itself." 
Autumn and mid-winter are, moreover, the best 



OF TRANSPLANTING, 283 

seasons, because of their great dampness. It will be 
seen bj reference to Mr. Thompson's tables (page 
183), that the air is very generally in a state of satura- 
tion in the months of October, November, December, 
January, and February, and that it is seldom in that 
condition at any other season. Now, although the 
perspiration of plants is greatly diminished by the 
removal of the leaves, it is not destroyed, for they 
also perspire through their young bark ; and there- 
fore a saturated atmosphere, which prevents much of 
the perspiratory action which remains from being ex- 
ercised, is a conditio-!, even when plants are leafless, 
much too beneficial to be overlooked. Nor is the ac- 
tion upon the perspLatory power of the stem the only 
mode in which a saturated atmosphere is important 
at the time of transplantation ; it exercises a directly 
favourable influence on the roots themselves. Roots, 
at their spongioles, or most absorbent points, are ex- 
tremely delicate parts, unprotected by a fully organis- 
ed epidermis* (22), destined to exist in a moist medium, 
and capable of being easily killed by exposure to dry- 
ness as well as by actual violence. The accidents to 
which the roots of transplanted trees are liable, from 
the very nature of the operation, are of such kind that 
it is impossible to prevent their being exposed to the 
air, sometimes for considerable periods of time ; it is 
therefore obviously a point of the first importance, 
that the air should be as nearly of the humidity of 
the soil from which the roots have been extracted as 
can be secured. How unfavourable, in this point of 
view, the months of March, April, and May are for 



284 APPLICATION OF PRINCIPLES. 

planting, is apparent from Mr. Thompson's tables 
above referred to ; how little the matter is attended 
to bj nurserymen, gardeners, and labourers, all great 
planters know to their cost. Mr. Macnab, who 
thoroughly understands all this, prefers a moist 
rainy day ; although, as he says, he has " at times 
been as wet in planting evergreens, as when exposed 
for hours on the windy side of Ben Nevis in a wet 
day, without greatcoat and with a broken umbrella." 
It may be very true that good plantations have been 
made in March and April ; it may be equally true 
that no such care as I have described is necessary for 
all plants ; but no wise man would, on that account, 
neglect the precautions which the nature of plants 
shows to be necessary to insure success with all things. 
Yery wet and late springs may prevent the loss of 
any considerable proportion of the trees planted in 
March and April, especially if succeeded by a dull, 
warm, wet summer ; and a Willow may be planted 
with success at midsummer : but we cannot tell be- 
forehand what sort of spring is coming, and all 
plants have not the tenacity of life possessed by a 
Willow. 

If the months of November and December are the 
most favourable for transplanting deciduous trees, 
and March and April the worst, how much more im- 
portant must be those periods to evergreens. An 
evergreen differs from a deciduous plant in this ma- 
terial circumstance, that it has no season of rest ; its 
leaves remain alive and active during the winter, and 
consequently it is in a state of perpetual growth. I do 



OF TRANSPLANTING. 285 

not mean that it is always lengthening itself in the 
form of new branches, for this happens periodically 
only in evergreens, and is "usually confined to the 
spring; bnt that its circulation, perspiration, assimi- 
lation, and production of roots are incessant. Such 
being the case, an evergreen, when transplanted, is 
liable to the same risks as deciduous plants in full 
leaf, with one essential difference. The leaves of ever- 
greens are provided with a thick hard epidermis (61), 
which is tender and readily permeable to aqueous ex- 
halations only when quite young, and which becomes 
very firm and tough by the arrival of winter, whence 
the rigidity always observable in the foliage of ever- 
green trees and shrubs. Such a coating as this is 
capable, in a much less degree than one of a thinner 
texture, such as we find upon deciduous plants, of 
parting with aqueous vapour; and moreover its 
stomates (61) are few, small, comparatively inactive, 
and chiefly confined to the under side, where they are 
less exposed to dryness than if they were on the upper 
side also. But although evergreens, from their struc- 
ture, are not liable to be affected by the same external 
circumstances as deciduous plants, in the same de- 
gree ; and although, therefore, transplanting an ever- 
green in leaf is not the same thing as transplanting a 
deciduous tree in the same condition, yet it must be 
obvious that the great extent of perspiring surface 
upon the one, however low its action, constitutes 
much difficulty, superadded to whatever difficulty 
there may be in the other case. Hence we are irre- 
sistibly driven to the conclusion, that whatever care 



286 APPLICATION OF PRINCIPLES. 

is required in the selection of a suitable season, damp, 
and not too cold, for a deciduous tree, is still more es- 
sential for an evergreen. It is, therefore, most extra- 
ordinary that it should ever have been the practice to 
defer the planting evergreens till late in the spring, 
upon the supposition that it is the very best season 
for them, and that midsummer even is a proper pe- 
riod ; as if cold winds, accompanied by from 20° to 
30° of dryness in the air, which is not more than 
•500 or *357 of moisture, with a bright sun beating 
on the roots which are exposed, and exciting the ac- 
tion of the perspiring surface to the utmost extent of 
its power, were external conditions with which the 
gardener has no concern : and yet, as Mr. Macnab 
justly observes, half a day's sun in spring and autumn 
will do more harm immediately after planting, than a 
whole week's sun from morning till night in the mid- 
dle of winter. 

The Holly, says the writer in the Horticultural 
Transactions, does not succeed well, if transplanted at 
any other season of the year than the end of April 
or beginning of May ; at this time the buds are just 
breaking open into leaf, and I have rarely failed of 
success in transplanting small, or even very large old, 
trees (ii. 357). Although such statements cannot be 
too strongly contradicted as guides to practice, yet it 
is not difficult to explain their origin. As evergreens 
are never deprived of their leaves, so they are never 
incapable of forming roots; on the contrary, they 
produce them abundantly all winter long, and rapid- 
ly at any other period of the year which is favourable 



OF TRANSPLANTING, 287 

to their growth : so that they are capable of making 
good an injury to their roots much more speedily than 
deciduous plants ; especially as in the majority of 
cases the roots are numerous and fibrous, and not so 
liable to extensive mutilation when transplanted. 
Now, if an evergreen is planted in the month of May, 
and the weather happens to be cloudy, mild, and 
damp, as the plant is just then commencing the re- 
newal of its growth, and is forming fresh roots abun- 
dantly, if such a state of weather lasts for a week or 
two, there is no doubt that the plant will succeed very 
well ; and so it will if removed at midsummer. In 
the year 1822, in the month of August, there were 
planted in the garden of the Horticultural Society of 
London above 6000 Hollies from two to three feet 
high, for the purpose of forming fences : few plants 
in all that number ever exhibited an}?- traces of hav- 
ing been removed, and I do not believe that a hun- 
dred died. The weather was dry ; but the plants 
were deluged with water when placed in their holes, 
and they had been obtained from the Eegent's Park, 
where they grew in the stiff plastic clay of that side 
of London ; the consequence of which was, that, when 
taken out of the ground, so much earth adhered to 
them, that they were almost in the state of plants re- 
moved from pots. Now, is this a case to justify 
planting Hollies in the month of August? Surely 
not ; it only shows that it may be done under a com- 
bination of very propitious circumstances. There 
may be local conditions of a permanent nature, owing 
to the peculiarity of climate, in which those advan- 



288 APPLICATION OF PRINCIPLES. 

tages maybe calculated upon; but they do not justify 
the gardener in taking a season of great risk, instead 
of a season of perfect certainty. I have seen tens of 
thousands of Hollies planted late in the spring in the 
county of Norfolk, and in the quarters, too, of nur- 
series, where, from the plants shading each other, they 
are far more likely to succeed than if exposed singly ; 
and although it sometimes happened that a good 
many lived, it is not too much to say that three-fifths 
at least would die ; and it is perfectly well known 
that if planted in the beginning of November no such 
loss is sustained. In short, I am certain that if ex- 
perience is looked to only, it will give the same an- 
swer as theory to the question of what season is the 
best for planting evergreens, namel}", that which is 
best for other trees ; and such cases to the contrary 
as may appear to exist will always be found excep- 
tions to the rule, in consequence of some peculiar cir- 
cumstances attending them ; not unfrequently, I be- 
lieve, from the operation having been performed upon 
a very small number of plants, to the removal of 
which a degree of care was given wholly incompatible 
with general and extensive practice." 

* [These remarks must be received with great modification, 
especially in the Northern and Eastern States. The moist or rainy 
winters of England are the exact opposite of our cold and dry ones, 
during which, for two months at lea<t, the soil is severely frozen, 
and vegetation is nearly or quite dormant. Our whole experience 
goes to prove that the practice of transplanting evergreens .in 
autumn is, for this country, extremely injudicious; as the damage 
which the trees sustain in their removal greatly increases their 
susceptibility to injury by the cold of winter. The early spring 



OF TRANSPLANTING. 289 

Mr. Macnab rightly adverts to the importance of 
choosing a suitable day, as well as season, for the 
operation ; and it must be evident from what has now 
been stated, and this is very necessary : as, however, 
the theory of this is the same as that of the season, it 
will be sufficient to quote this excellent practical gar- 
dener's rule. In winter, you may plant with perfect 
safety in a dull calm day, whereas in spring or autumn 
a moist rainy day is preferable to any other; but 
where a person has not the choice of such weather, 

is the most favourable period for the purpose ; since the abundant 
and long-continued rains which occur from the vernal equinox to 
the middle of April enable the plant to recover itself, and emit 
new roots with rapidity. We have been very successful in May, 
but then so much depends upon the occurrence of rainy weather, 
that the risk is greatly increased. Next to the selection of the 
proper time, the preservation of the roots in a moist condition is 
the most essential point, in removing all evergreen trees. — These 
remarks are not applicable to a different mode of transplanting 
large evergreen and other trees, which is very successfully prac- 
tised in this country ; that of removing them with large frozen 
balls of earth in midwinter. The trees to be removed are selected, 
and the holes prepared for their reception in autumn, while the 
ground is yet open. When the ground is slightly frozen, the ope- 
rator proceeds to dig a trench around the tree, at some distance 
from its trunk, gradually undermining it, and leaving the princi- 
pal mass of roots embodied in the ball of earth, which is left to 
freeze pretty thoroughly. At a favourable time during the win- 
ter, the tree with the ball of frozen earth is rolled upon a sled 
drawn by oxen, by which it is readily transferred to the hole 
previously prepared for its reception, and placed in the proper 
position ; and as soon as the weather becomes milder, the earth 
is properly filled in around the ball. In this way, a tree twenty- 
five feet high may be transplanted, so as scarcely to exhibit, during 
the ensuing season, any ill effects from the change of location. A J. D, 

13 



290 APPLICATION OF PRINCIPLES. 

then the work should be performed in the evening, 
when the sun gets low, especially in spring or autumn 
planting. 

Next in importance to the selection of a fitting sea- 
son, is the preservation of the roots of transplanted 
trees ; the former is of little consequence, if the latter 
is not more carefully attended to. We know, indeed, 
that some plants will live with the rudest treatment, 
and bear the most severe mutilation without much 
suffering ; but those are special instances of extreme 
tenacity of life, and do not affect general principles. 
The value of great attention to the roots, in the ope- 
ration of shifting, has already been pointed out (p. 
269), and transplanting is only shifting in another 
manner. It would be the duty of the gardener to 
save every minute fibre of the roots, if it were prac- 
ticable ; but, as that is not the case, his care must be 
confined to lifting his trees with the least possible 
destruction of those important organs; remembering 
always that it is not by the coarse old woody roots 
that the absorption of food is carried on, but by the 
younger parts, and especially the spongioles (23,24.) 
The mechanical means by which this is best effected 
do not belong to the present subject ; I may, how- 
ever, remark, without quitting the limits of theory, 
that, as the greater part of the young fibres is pro- 
duced at the circumference of the circle formed by 
the root, the earth should be first removed at some 
distance from the stem, so as to insure, as far as pos- 
sible, their being. taken up entire ; if this is not done, 
but the spade is struck into the earth near the stem, 



OF TRANSPLANTING. 291 

or if the rude nursery practice, justly enough called 
drawing, is employed, a large part of the most valua- 
ble roots must necessarily be cut off or destroyed by 
tearing. The greatest difficulty, beyond that of 
mechanical removal, in transplanting trees of consi- 
derable size, is this preservation of roots ; and, if it 
were possible to carry without injury such heavy 
masses as old forest trees, there is no physical obstacle 
to transplanting them, if the extrication of the fibrous 
part of the roots be secured, which is not impracti- 
cable. As, however, the latter is a troublesome and 
very difficult operation, even when trees are only ten 
or twelve feet high, it has been, from time out of 
mind, the custom of skilful planters to prepare such 
trees for removal by cutting back their main roots 
one year before they are to be transplanted ; if this 
very simple operation is properly performed, all the 
principal limbs, so amputated, will emit young fibres 
in abundance from their extremities, and the gardener, 
from knowing where to find those roots, can easily 
take them up without material injury. In order to 
effect the same end, but in another way, the following 
expedient has been occasionally employed for large 
trees. A deep trench has been opened, in midwinter, 
round a stem, at such a distance as to be clear of the 
principal fibres ; the tree has then been carefully 
undermined, till, at last, the earth belonging to it has 
formed a huge ball ; upon the approach of frost, 
water has been freely poured over the ball so that its 
whole surface may be converted into an icy mass ; in 
that state it has been raised by powerful tackle, and 



292 APPLICATION OF PRINCIPLES. 

conveyed without disturbance to its intended site. 
This operation, which is the best possible for hardy- 
trees of great size, but expensive, and therefore only 
capable of application in a limited degree, owes its 
success entirely to the young and tender fibres being 
placed in such a position that they cannot be injured 
by the act of transport. 

Under all ordinary circumstances, the roots must 
necessarily be injured more or less by removal ; in 
that case, all the larger wounds should be cut to a 
clean smooth face ; not in long ragged slivers, as is 
often the case, and which is only substituting one 
kind of mutilation for another, but at an angle of 
about 45°, or less. If the ends of small roots are 
bruised, they generally die back a little way, and 
then emit fresh spongioles; but the larger roots, when 
bruised, lose the vitality of their broken extremity, 
their ragged tissue remains open to the uncontrolled 
introduction of water, decays in consequence of being 
in contact with an excess of this fluid, and often 
becomes the seat of disease which spreads to parts 
that would otherwise be healthy. When, however, 
the wound is made clean by a skilful pruner, the ves- 
sels all contract, and prevent the introduction of an 
excess of water into the interior ; the wound heals by 
granulations formed by the living tissue, and the 
readiness with which this takes place is in proportion 
to the smallness of the wound. It may be sometimes 
advantageous to remove large parts of the coarser 
roots of a tree, even if they are not accidentally 
wounded when taken up, the object being to compel 



OF TRANSPLANTING. 298 

the plant to throw out, in room of those compara- 
tively inactive subterranean limbs, a supply of young 
active fibres. This is a common practice in the nur- 
series in transplanting young Oaks and other tap- 
rooted trees, and is one of the means employed by 
the Lancashire growers of Gooseberries, in order to 
increase the vigour of their bushes ; in the last case, 
however, the operation is not confined to the time 
when transplantation takes place, but is practised 
annually upon digging the Gooseberry borders. The 
reason why cutting off portions of the principal roots 
causes a production of fibres appears to be this : the 
roots are produced by organisable matter sent down- 
wards from the stem (31) ; that matter, if uninter- 
rupted, will flow along the main branches of the 
roots, until it reaches the extremities, adding largely 
to the wood and horizontal growth of the root, but 
increasing, in a very slight degree, the absorbent 
powers : but if a large limb of the roots is ampu- 
tated, the powers of the stem remaining the same, 
all that descending organisable matter which would 
have been expended in adding to the thickness of the 
amputated part is arrested at the line of amputation ; 
and, unable to pass further on. rapidly produces gra- 
nulations to heal the wound, and immediately after- 
wards young spongioles, which soon establish them- 
selves in the surrounding soil, and become the points 
of new active fibres. 

The question of pruning the branches of trans- 
planted trees has been already sufficiently adverted 
to (see p. 248). 



294 APPLICATION OF PRINCIPLES. 

By many excellent planters, the advantage of de- 
luging the roots with water, when newly planted, is 
much insisted on : and in the case of large plants, 
particularly evergreens, it is, undoubtedly, an essen- 
tial process, partly because it causes the flagging and 
injured roots to be immediately surrounded by an 
abundant supply of liquid food, which, if the opera- 
tion be skilfully performed (see Macnab's Treatise, p. 
24 and 25), will not subsequently fail them; and 
partly because it is the only means we possess of 
embedding with certainty all the fibres in soil. 
When the earth is reduced to the state of puddle, it 
will settle round the finest roots, and place them as 
nearly as possible in the same condition, with regard 
to the soil, that they were in before the plants were 
removed. But the operation of puddling is unneces- 
sary to small plants, if removed at a proper season 
of the year, especially to deciduous trees of all kinds ; 
and it may be very injurious. This was long ago 
stated by Mr. Knight (Hort. Trans., iii. 159), who 
found by experience that when trees are very much 
out of health, in consequence of having become dry, 
excess of moisture to the roots is often fatal. This 
appears to arise from the languid powers of the 
plant being insufficient to enable it to decompose and 
assimilate the water rapidly introduced into its system 
through the wounds in its root, and by the hygrome- 
trical force of that part ; under such circumstances, 
water will dissolve the mucilaginous and other mat- 
ters intended for the support of the nascent buds, 
which matters then putrefy, lose their nutritive qua- 



PRESERVATION OF RACES BY SEED. 295 

lity, and rapidly destroy the tissue. The substitute 
for root- watering contrived by Mr. Knight in such 
cases was, to keep the plants in a situation shaded 
from the morning sun, and to moisten their bark fre- 
quently ; by these means, water is presented to them 
very slowly through the young cortical integument 
(48) ; which, partaking of the nature of a leaf (63), 
slowly absorbs it, probably decomposes it, and trans- 
mits it laterally (57) through the liber into the albur- 
num, where it finds itself in the ordinary channel for 
the ascending sap, and thus enters the system of 
circulation. In this way Mr. Knight originally pre- 
served American Apple trees, which reached him in 
the middle of April, in so bad a state that they seemed 
"perfectly lifeless and dry, and much better fitted for 
firewood than for planting."* 



CHAPTEE XVII. 
OF THE PRESERVATION OF RACES BY SEED. 

The manner of preserving the domesticated races 

* For the same reason, the best possible mode of reviving trees 
that have become dry and shrivelled by long transportation is to 
unpack them and bury them for a few days in light soil, covering 
both roots and branches with earth. The parched bark will absorb 
moisture gradually from the earth, and the trees may be entirely 
restored to freshness and vitality, when immersing them in water, or 
planting them with the branches dry, would only insure their death. 
A. J. D. 



296 APPLICATION OF PRINCIPLES. 

of plants by the ordinary means of propagation, such 
as cuttings, layers, grafts, and so on, has already been 
explained ; there are, however, some other topics con- 
nected with this important subject which require to 
be touched upon. 

Propagation by division is inapplicable to annuals 
or biennials, or at least can be practised upon only a 
very limited scale, and for such plants the gardener 
has to trust to seeds alone. But it is an axiom in 
vegetable physiology that seeds reproduce the species 
only, while buds (that is, propagation by division) 
will multiply the variety; and this is undoubtedly 
true as a general rule. But the skill and care of the 
gardener often enable him to perpetuate by seed the 
many races of cultivated annuals, varieties of the same 
species, improved and altered by centuries of domes- 
tication, with as much certainty as if he were operat- 
ing with cuttings. In a well managed farm we see the 
various breeds of Turnips and Corn preserving each 
its own peculiar character unchanged year after year, 
and yet they must all be propagated by seed alone ; 
and in gardens the varieties are innumerable of Peas, 
Lettuces, Cabbages, Eadishes, &c, whose purity is 
maintained by the same means. The manner in 
which this is effected is of the first importance to be 
understood. 

Although it is the general nature of a seed to per- 
petuate the species only to which it belongs, and it 
cannot therefore be relied upon, in ordinary cases, to 
renew a particular variety of species, yet there is al- 
ways a visible tendency in it to produce a seedling 



PRESERVATION OF RACES BY SEED. 297 

more like its parent than any other form of the 
species. Suppose, for example, the seed of a Eibston 
Pippin apple were sown ; if untainted by intermixture 
with other varieties, it would produce an apple tree 
whose fruit would be large, sweet, and agreeable to 
eat, and not small, sour, and uneatable, like the 
Wilding Apple or Crab. The object of the gardener 
is to fix this tendency, and he does it by means not 
unlike those employed in the preservation of the races 
of domesticated animals, namely, by " breeding in and 
in," as the phrase is. An example of this will be more 
instructive than a dissertation. The Eadish has, when 
wild, a long pallid root ; among many seedlings one 
was remarked with roots shorter and rounder, and 
more succulent than the remainder; this was a " sport" 
to which all plants are subject. Had that Eadish 
been left among its companions, and the seed saved 
from them all indifferently, the tendency would have 
disappeared for that time ; but its companions were 
all eradicated, and the better one produced its seed in 
solitude. The crop of young plants produced from 
this Eadish was, for the most part, composed of indi- 
viduals of the wild form, but several preserved the 
same qualities as the parent, and some, perhaps 
one only, in a higher degree : in this one, then, the 
tendency was beginning to fix. Again were all 
eradicated, except the last-mentioned individual, 
whose seeds were carefully preserved for the succeed- 
ing crop ; and, by a constant repetition of this prac- 
tice for many years, at last the habit to produce a 
round and succulent root became so fixed, that all the 
13* 



298 APPLICATION OF PRINCIPLES. 

Radishes assumed the same appearance and quality, 
and there were none left to draft or " rogue." Every 
variety of annual crop, not still in its wild state, must 
have gone through this process of fixing ; and thus 
the varieties of earliness, lateness, and productive- 
ness, colour, form, and flavour, observable in garden 
plants, have been secured for our enjoyment. 

But to fix a new habit in annual plants is not the 
only care of the cultivator, whose patience and skill 
would be ill employed if it could not be preserved. 
If a plant has some tendency to vary from its origi- 
nal condition, it has much more to revert to its wild 
state ; and there can be no doubt that, if the arts of 
cultivation were abandoned for only a very few years, 
all the annual varieties of our gardens would disap- 
pear, and be replaced by a few original wild forms. 

For the means of preserving the races of plants 
pure, the means vary according to the nature of the 
variety. As far as concerns early and late varieties, 
it often happens that, as in Peas, the tendency in such 
plants to advance or retard their season of ripening 
was originally connected with the soil or climate in 
which they grew. A plant which for years is culti- 
vated in a warm dry soil, where it ripens in forty 
days, will acquire habits of great excitability ; and, 
when sown in another soil, will, for a season or so, 
retain its habit of rapid maturity : and the reverse 
will happen to an annual from a cold wet soil. But, 
as the latter will gradually become excitable and 
precocious, if sown for a succession of seasons in a dry 
warm soil, so will the former lose those habits, and 



PRESERVATION OF RACES BY SEED. 299 

become late and less excitable. Hence, the best 
seedsmen always take care that their early varieties 
of annuals are procured from warmer and drier lands 
than those on which they are to be sown ; our earliest 
Peas, for example, are obtained from France, and the 
next in time of ripening from the hot dry fields of 
Kent, the Suffolk coast, and similar situations. Thus, 
also, the Barley grown on sandy soils, in the warmest 
parts of England, is always found by the Scotch 
farmer, when introduced into his country, to ripen on 
his cold hills earlier than his crops of the same kind 
do, when he uses the seeds of plants which have 
passed through several successive generations in his 
colder climate - ; and Mr. Knight found that the crops 
of Wheat on some very high and cold ground, which 
he cultivated, ripened much earlier when he obtained 
his seed-corn from a very warm district and gravelly 
soil, which lies a few miles distant, than when, he em- 
ployed the seed of his vicinity. It would seem as if 
this were in some way connected with the mere size 
of a seed, the smallest seeds of a given variety pro- 
ducing plants capable of fructifying quicker than 
those of a much larger size. We have, at present, 
but little information upon this subject; but there 
are some most curious experiments relative to it by 
Messrs. Edwards and Colin, who found that, although 
Winter Wheat cannot, in France, be made to shoot 
into ear, if sown in the spring, provided the largest 
grains of the variety are employed, yet that, if the 
smallest grains are picked out, some will ear like 
Spring Wheat (see Annates des Sciences Naturales, v. 



300 APPLICATION OF PKLXCIPLES. 

1). Out of 530 grains of Winter Wheat, sown on the 
23d of April, and weighing 7 ounces 52 grains, not 
one pushed into ear ; they tillered abundantly, but the 
tillers were excessively stunted, and concealed among 
the tufts of leaves ; in short, they formed nothing but 
turf: on the other hand, of 530 other grains, weigh- 
ing 3 ounces 56 grains, and sown on the same day, 
60 pushed in ear. 

It would seem as if many of our most esteemed 
garden plants were the result of debility, and that the 
succulence, the sweetness, or the excessive size, which 
render them so well suited for food, were only marks 
of unhealthiness. At least, it is almost necessary to 
assume this to be the case, in order to account for 
the efficacy of one of the modes of maintaining races 
genuine. It is perfectly well known, that, if such an 
annual as a Turnip is transplanted shortly before it 
runs to seed, the characters of its variety will remain 
more strongly marked, and have far less tendency to 
vary, than if, all other circumstances remaining the 
same, the seed is saved without the process of trans- 
plantation having been observed. Now, the only 
effect of transplanting, at the season immediately pre- 
ceding the formation of a flower-stalk, would seem to 
be that of checking the luxuriance of the individual 
operated on ; or, upon the above assumption, of in- 
creasing its debility of constitution. And the same 
explanation appears applicable to a strange custom 
mentioned by Mr. Ingledew as being practised in the 
Dekkan, to prevent the rapid deterioration, in that 
climate, of the Carrot, the Radish, and the Parsnep, 



PRESERVATION OF RACES BY SEED. 801 

the favourite table vegetables of the inhabitants. He 
states that the Indian gardeners, in the first place, 
prepare a compost of buffaloes' dung, swine's dung, 
and red maiden earth, mixed with water till thej have 
the consistence of paste, and scented with a small 
quantity of assafoetida, the latter of which seems to be 
perfectly useless. 

" The vegetables for this operation are drawn, 
when wanted, from the beds, when they have attain- 
ed about one third of their natural growth, and those 
plants are chosen which are the most succulent and 
luxuriant ; the tops are removed, leaving a few inches 
from their origin in the crown upwards ; and a little 
of the inferior extremity, or taproot, is cut straight 
off likewise, allowing nearly the whole of the edible 
part to remain, from the bottom of which to within 
about an inch of the crown, are made two incisions 
across each other entirely through the body of the 
vegetable, dividing it into quarters nearly to the up- 
per end. They are then dipped into the compost 
until they are well covered by it, both externally and 
internally, and are immediately placed in beds, pre- 
viously prepared for their reception, at the distance 
of fifteen or sixteen inches from each other, and so 
deep in the ground that the upper extremities only 
appear in sight. They are afterwards regularly 
watered ; and when they take root, and fresh tops 
have made some advance in growth, they require but 
little attention. The tops speedily become large, and 
grow into strong and luxuriant stalks, the blossoms 
acquire a size larger than ordinary, and the seed they 



302 APPLICATION OF PRINCIPLES. 

produce is likewise large and vigorous, and supera- 
bundant in quantity. Innumerable roots are thrown 
out from the incised edges of these plants ; they con- 
sequently receive a greater abundance of nourishment, 
which occasions their luxuriant growth, causes them 
to }deld not only a more than ordinary crop of seed, 
but also of a superior quality. (Hort. Trans. , v. 517.) 
The operation is performed at the beginning of the 
dry season. 

Besides " roguing out" (i. e. eradicating) all indivi- 
duals having the slightest appearance of degeneracy 
from among the plants intended for seed, care must 
be taken that the crop is so far from any other of a 
similar kind as to incur no risk of being spoiled by the 
intermixture of its pollen (88). This substance is 
conveyed to considerable distances by wind and in- 
sects ; and it is scarcely possible to be secure from its 
influence, if similar crops are cultivated within some 
miles of each other ; whence we find certain villages, 
in different parts of Europe, celebrated for the purity 
of the seed of particular varieties ; this usually happens 
in consequence of the villagers cultivating that 
variety and no other, as happens at Castelnaudary 
with Beet, at Altringham with the Carrot, and in 
Norfolk with different kinds of Turnip. 

It is, however, to be observed, that the deteriora- 
tion of seed by bastardising happens to a greater 
extent to single plants than to large masses of them ; 
and it seldom happens that good seed can be saved 
in a garden, or near gardens, from a single indivi- 
dual. Solitary specimens of the Turnip, the Cauli- 



PRESERVATION OF RACES BY SEED. 34)3' 

flower, and such plants, have been frequently selected 
on account of their perfect characters, and been care- 
fully planted in gardens for a stock of seed, but their 
produce has as frequently been of the worst descrip- 
tion, bearing no resemblance to the parent. In such 
cases as these, it would seem as if bees and other 
insects were attracted from all quarters by the gay 
colours, or odour, of such isolated individuals, and, 
arriving from a hundred flowers which they had pre- 
viously visited, bring with them so many sources of 
contamination. 

When, however, the action of other flowers can be 
prevented, as in the Melon and other unisexual 
plants, by " setting," the largest, healthiest, and most 
cultivated varieties will yield seed of the purest and 
finest quality. The tendency of Persian Melons to 
degenerate in this country was remarked soon after 
their introduction; and, for a long time, it was 
thought impossible to preserve them for many 
generations. Mr. Knight, in his numberless experi- 
ments upon this fruit, found that to be the case ; for 
his fruit, at one time, became less in bulk and weight, 
and deteriorated in taste and flavour. But when he 
came to consider that " every large and excellent 
variety of Melon must necessarily have been the pro- 
duction of high culture and abundant food, and that 
a continuance of the same measures which raised 
it to its highly improved state must be necessary 
to prevent its receding, in successive generations, 
from that excellence," the cause of his Persian Melons 
deteriorating became apparent ; and he found that by 



304 APPLICATION OF PRINCIPLES. 

"bringing the cultivation of the plants to a state 
of great perfection, he succeeded completely in ren- 
dering the original quality hereditary, so long as 
those precautions were observed. No man was more 
successful in the cultivation of the Melon than Mr. 
Knight ; and it is in the memory of many persons, 
that the quality of his Sweet Melons of Ispahan has 
very rarely been equalled. The peculiar methods 
that he adopted appear to have been the complete 
and most careful preservation of the leaves from 
injury of whatever kind, the full exposure of their 
surface to light, and the augmentation of the ordinary 
warmth of a Melon bed by availing himself of the 
heat reflected from brick tiles with which his bed 
was paved. To such an extent was his care of the 
leaves carried, that he would not allow even the 
watering to be performed " over-head," but he caused 
his gardener to pour water, from a vessel of proper 
construction, upon the brick tiles between the leaves, 
without touching them. (See various papers upon 
the Melon in the Horticultural Transactions, and espe- 
cially that in vol. vii. p. 684:.) 

While, however, such are the general principles 
upon which the preservation of the peculiar qualities 
of the many races of cultivated annuals necessarily 
depends, it must be confessed that, according to 
report, there are circumstances upon which science 
can throw no light, and which, if true, must depend 
upon conditions as yet unsuspected to exist. Of this 
class is the following, respecting the Brussels Sprouts 
Cabbage, given upon the authority of M. Van Mons. 



PRESERVATION OF RACES BY SEED. 805 

"Much has been said of the disposition of this 
plant to degenerate. In the soil of Brussels it 
remains true, and I have lately observed it to do the 
same at Louvain ; but at Malines, which is the same 
distance from Brussels as Louvain, and where the 
greatest attention is paid to the growth of vegetables, 
it deviates from its proper character, after the first 
sowing ; yet it does not seem that any particular soil 
or aspect is essential to the plant, for it grows equally 
well and true at Brussels, in the gardens of the town, 
where the soil is sandy and mixed with a black moist 
loam, as in the fields, where a compact white clay 
predominates. The progress of deterioration at 
Malines was most rapid ; the plants raised from seed 
of the true sort, which I had sent there, produced the 
sprouts in little bunches or rosettes, in their true 
form ; seeds of those being saved, they gave plants in 
which the sprouts did not form into little cabbages, 
but were expanded ; nor did they shoot again at the 
axils of the stem. The plants raised from the seeds 
of these last mentioned only produced lateral shoots 
with weak pendant leases, and tops similar to the 
shoots, so that in three generations the entire charac- 
ter of the original was lost. From a plant in the state 
last described, seed was saved at my request, and 
sent back to me. I had it sown by itself, and care- 
fully watched the plants in their growth ; I was not 
long in discovering that they retained the same cha- 
racter of degeneration they had assumed at Malines, 
and preserved it throughout the whole course of their 
growth, yielding pendulous leaves with long petioles, 



306 APPLICATION OF PRINCIPLES. 

and having no disposition to cabbage. I suffered 
these plants to run to seed at a great distance from 
my true Sprouts, which the extent of my garden 
allowed me easily to do. The second sowing brought 
them back a good deal to their true character ; the 
plants yielded small cabbages regularly at each axil, 
but not generally full or compact, and they did not 
shoot a second time, as the true sort does. I again 
suffered these to run to seed, using the same precau- 
tion of keeping them by themselves. I sowed the 
seed, and this time the plants were found to have 
entirely recovered their original habits, their head, 
and rich produce." (Hort. Tra?is. 1 iii. 197.) I must 
confess, however, that, although the passage merits 
quotation, for the sake of exciting attention to the 
subject, it appears to me very doubtful whether the 
case has been fully, if correctly, stated. 



CHAPTEK'XVIII. 

OF THE IMPROVEMENT OF RACES. 

What has been stated in the preceding chapter, 
concerning the preservation of the races of domes- 
ticated plants, is in some measure applicable to their 
improvement, because the very means employed 
to preserve those peculiarities of habit which render 
them valuable, will, from time to time, be the cause 
of still more valuable qualities making their appear- 



OF THE IMPROVEMENT OF RACES. 307 

ance. There are, however, other points of great 
importance on which the gardener has dependance. 

A fixed improvement in the quality of the produce 
of a plant can only be obtained in one of two ways ; 
either directly, by accidental variations in itself, or 
indirectly, by the process of muling. 

Direct alterations in the quality of seedling plants 
often occur from no apparent cause, just as those ac 
cidental changes, called "sports," in the colour or form 
of the leaves, flowers, or fruit, of one single branch 
of a tree, occasionally break out, we know not why. 
Of these things, physiology can give no account ; but 
it is known that, when those sports appear, they in- 
dicate a permanent constitutional change in the action 
of the limb thus affected, which changes may be 
sometimes perpetuated by seed, and always by pro- 
pagation of the limb itself, when propagation is prac- 
ticable. It is in this way that many of our fruits have 
probably, and several of the Chinese Chrysanthemums 
have certainly, been obtained. It was apparently 
thus that the Nectarine emanated from the Peach. It 
is possible that many new forms of shrubs might be 
procured by keeping these facts in view, and that 
climbers might be deprived of their climbing habits ; 
for it is known that the handsome evergreen bush 
called the Tree Ivy, which grows erect, with scarcely 
the least tendency to climb, has been procured by 
propagating the fruit -bearing branches of trees of con- 
siderable age. 

But we are by no means destitute of the power of 
procuring, with considerable certainty, improved 



308 APPLICATION OF PRINCIPLES. 

varieties, by an application to practice of physiologi- 
cal principles. In the last chapter has been shown 
the importance of securing the production of seed by 
plants in the most healthy state possible, because a 
robust parent is likely to afford a progeny of similar 
habits to itself. In annuals, however, this is appa- 
rently restrained within narrower limits than in woody 
plants, from the great difficulty of fixing a new 
peculiarity in the former, and the facility with which 
it may be effected in the latter case, by means of 
buds, cuttings, grafts, and similar modes of propaga- 
tion. The great object of the scientific gardener who 
desires to improve the varieties of plants upon prin- 
ciple will be, then, by artificial means, to bring the 
parent from which seed is to be saved as near as pos- 
sible to that state at which he desires the seedling to 
arrive. 

It is well known that the abstraction of fruit and 
flowers augments the vigour of the branches, or of the 
parts connected with them, and that the removal 
from the former of any part which takes up a portion 
of the food employed in the support of the flowers in- 
creases their efficiency. Thus those varieties of the 
Potato, which will neither flower nor fruit otherwise, 
may be made to do both by stopping the develope- 
ment of tubers; and, on the other hand, the size 
and weight of the tubers themselves are increased by 
preventing the formation of flowers and fruit. The 
course, then, to .take, in obtaining the largest possible 
tubers in a new variety of the Potato, would be, in 
the first place, to effect that end temporarily, but dur- 



OF THE IMPROVEMENT OF RACES. 309 

ing several successive seasons, by abstracting all the 
flowers and fruit, and by such other means as may 
suggest themselves • and then to obtain the most per- 
fect seed possible by a destruction of the tubers dur- 
ing the season when seed is finally to be saved. Mr. 
Knight found, in raising new varieties of the Peach, 
that, when one stone contained two seeds, the plants 
these afforded were inferior to others. The largest 
seeds obtained from the finest fruit, and from that 
which ripens most perfectly and most early, should 
always be selected {Hort. Trans., i. 39) ; and, in his 
incessant efforts to obtain new varieties of fruit of 
other genera, he had reason to conclude that the trees, 
from blossoms and seeds of which it is proposed 
to propagate, should have grown at least two years in 
mould of the best quality ; that during that period 
they should not be allowed to exhaust themselves by 
bearing any considerable crop of fruit ; and that the 
wood of the preceding year should be thoroughly 
ripened (by artificial heat when necessary) at an early 
period in the autumn ; and, if early maturity in the 
fruit of the new seedling plant is required, that the 
fruit, within which the seed grows, should be made to 
acquire maturity within as short a period as is consis- 
tent with its attaining its full size and perfect flavour. 
Those qualities ought also to be sought in the parent 
fruits, which are desired in the offspring; and he 
found that the most perfect and vigorous progeny was 
obtained, of plants as of animals, when the male and 
female parent were not closely related to each other. 
(See the Horticultural Transactions, i. 165.) 



310 APPLICATION OF PRINCIPLES. 

There are no processes known to the cultivator so 
efficacious in producing new varieties as that adverted 
to in the last paragraph, that is to say, muling or cross 
breeding (88) ; and it is to these operations, more than 
to any thing else, that we owe the beauty and excel- 
lence of most of our garden productions ; more, how- 
ever, I think, to cross breeding than to muling. It 
was entirely by the first of these processes that have 
been so greatly multiplied and improved our fruits 
for the dessert, and the gay flowers that adorn our 
gardens. The Pelargonium, the Calceolaria, the 
Dahlia, the Verbena, and a thousand others — what 
would they be but simple wild flowers, without the 
power of man exercised in this way ? "To the cul- 
tivators of ornamental plants," says Mr. Herbert,* 
"the facility of raising hybrid varieties affords an 
endless source of interest and amusement. He sees 
in the several species of each genus that he possesses 
the materials with which he must work, and he con- 
siders in what manner he can blend them to the best 
advantage, looking to the several gifts in which each 
excels, whether of hardiness to endure our seasons, 
of brilliancy in its colours, of delicacy in its mark- 
ings, of fragrance, or stature, or profusion of blossom ; 
and he may anticipate, with tolerable accuracy, the 
probable aspect of the intermediate plant which he is 
permitted to create ; for that term maj- be flgurative- 

* See much the most valuable and practical account of cross 
breeding and muling which has been yet published in regard to 
horticulture, in the Amaryllidaceai of the Hon. and Rev. W". 
Herbert, p. 335, et seq. 



OF THE IMPROVEMENT OF RACES. 311 

ly applied to the introduction into the world of a na- 
tural form which has probably never before existed 
in it. In constitution the mixed offspring appears to 
partake of the habits of both parents ; that is to say, 
it will be less hardy than the one of its parents which 
bears the greatest exposure, and not so delicate as the 
other; but, if one of the j^arents is quite hardy, and 
the other not quite able to support our winters, the 
probability is, that the offspring will support them, 
though it may suffer from a very unusual depression 
of the thermometer, or excess of moisture, which 
would not destroy its hardier parent." 

In the many successful attempts made by Mr. 
Knight to improve the quality of fruit trees by rais- 
ing new varieties, his method was to obtain cross- 
breds by fertilising the stigma of one variety of 
known habits with the pollen of another also of 
known habits. But, in doing this, his experiments 
were not conducted at random, and without due con- 
sideration ; on the contrary, we learn from himself 
that he was very careful in selecting the parents from 
which his crossbreds were obtained. He found that 
the general opinion, that the offspring of crossbred 
plants as well as crossbred animals usually presents 
great irregularity of character, is unfounded ; and 
that if a male of permanent habits, and of course not 
crossbred, be selected, that will completely overrule 
the disposition to sport, " the permanent character 
always controlling and prevailing over the variable." 
He tells us that he usually propagated from the seeds 
of such varieties as are sufficiently hardy to bear and 



312 APPLICATION OF PRINCIPLES. 

ripen their fruit, even in unfavourable seasons and 
situations, without the protection of a wall, because, 
in many experiments made with a view to ascertain- 
ing the comparative influence of the male and female 
on their offspring, he had observed in fruits, with few 
exceptions, a strong prevalence of the constitution 
and habits of the female parent. Unfortunately, 
however, this is precisely the reverse of the result at 
which Mr. Herbert has arrived in the very great 
number of experiments performed by himself on that 
subject, he believing that the male parent generally 
influences the character of the foliage, and the female 
that of the flowers (Amaryllidacetp, p. 348, 377) ; and 
although it does appear to me that, in the majority 
of cases, Mr. Herbert's opinion is the more correct of 
the two, yet I fear there is too little certainty in the 
results of hybridising to justify the establishment of 
any axiom upon the subject. 

This power of muling, property so called, is con- 
fined within very narrow limits, and can hardly be 
said to exist at all between species of different genera, 
unless under that name are comprehended some of 
the spurious creations of inconsiderate botanists. 
There are, indeed, many cases of species very closely 
allied to each other which it is eicher impossible 
to mule, or so difficult that no one has yet succeeded 
in effecting it. Mr. Knight never could make the 
Morello breed with the common Cherry. I have in 
vain endeavoured to mule the Gooseberry and Cur- 
rent, and we do not possess any garden production 
known to have been produced between the Apple 



OF THE IMPROVEMENT OF RACES. 313 

and the Pear, or the Blackberry and the Kaspberry, 
any of which might have been expected to intermix. 
As to mules obtained between plants of distinct 
genera, we have, no doubt, upon record, some experi- 
ments said to have been performed successfully in 
crossing a Thorn- Apple with Tobacco, the Pea with 
the Bean, the Cabbage with the Horse-radish, and so 
on; but Mr. Herbert regards these cases, and I think 
with great reason, as apocryphal, and not to be relied 
on ; the fact being, as he truly states, u that in this 
country, where the passion for horticulture is great, 
and the attempts to produce hybrid intermixtures 
have been very extensive during the last fifteen years, 
not one truly bigeneric mule has been seen." 

On the other hand, cross breeding (89) will take 
place quite as readily among plants as among ani- 
mals, and it is difficult to estimate the alteration 
which this process has really produced, although 
unperceived by us, in the amelioration and advantage 
of long-cultivated plants. We cannot reasonably 
doubt that a process so simple as that of dusting the 
stigma of one plant with the pollen of another, which 
must be continually happening in our gardens, either 
through the agency of insects or the currents in the 
air, and which, where it takes place between two 
varieties allied to each other, must necessarily pro- 
duce a cross, — we cannot suppose, I say, that this 
occurs in our crowded gardens and orchards at that 
time only when we perform it artificially. 

The operation itself, although so simple, consisting 
in nothing more than applying the pollen of one 
14 



314 APPLICATION OF PRINCIPLES. 

plant to the stigma of another, nevertheless requires 
to be guarded by some precautions. In the first 
place, it is requisite that the flower whose stigma 
is to be fertilised should be deprived of its own 
anthers before they burst, otherwise the stigma will 
be self-impregnated, and although superfcetation is 
not, by any means, impossible, yet it is not very 
likely to occur. Then, again, the application of the 
stranger pollen should be made at the time when the 
stigma is covered with its natural mucus ; if not, the 
pollen will not act, either in consequence of the 
necessary lubrification of itself being withheld, from 
the stigma being too young, or because the stigma, 
from age, has lost its power of receiving the action 
of the pollen. Neither should the stigma be in any 
way injured after fertilisation has apparently taken 
place. The art of fertilisation consists in the emission, 
by the pollen, of certain tubes of microscopical tenuity, 
which pass down the style, and eventually reach the 
young seed, with which they come in contact ; and, un- 
less this contact takes place, fertilisation misses. Now 
the transmission of the pollen tubes from the stigma 
to the ovule, through the solid style, is often very 
slow, sometimes occupying as much as a month or six 
weeks, as in the Misletoe. 

Those who occupy themselves in attempts at 
improving the quality of cultivated plants should be 
aware of this : namely, that the real quality of either 
the fruit or the flower of a seedling cannot be ascer- 
tained w r hen they are first produced ; for it is only as 
plants advance in age that the secretions necessary 



OF THE IMPROVEMENT OF RACES. 315 

for the perfect production of either the one or the 
other are elaborated. Of this fact, the first produce 
of the Black Eagle Cherry tree afforded a striking 
example. A part of it was sent, with other cherries, 
to the Horticultural Society ; and it was then, in the 
Fruit Committee, pronounced good for nothing. It 
was so bad, that Mr. Knight, who raised it, would 
most certainly have taken off the head of the tree 
and employed its stem as a stock, but that it had been 
called the property of one of his children, who sowed 
the seed which produced it, and who felt very anxious 
for its preservation. It has now become one of the 
richest and finest fruits of its species which we pos- 
sess. 

It may be expected that some mention should here 
be made of double flowers, and of the manner in 
which they are to be obtained. But I confess myself 
unable to discover, either in the writings of physiolo- 
gists, or in the experience of gardeners, or in the 
nature of plants themselves, any sufficient clue to an 
explanation of the causes to which their origin may 
be ascribed. There are, however, several facts ap- 
parently connected with the subject, which deserve 
mention. 

A double flower, properly so called,* is one in 
which the natural production of stamens or pistils is 

* What is called a Double Dahlia is misnamed; and so are 
all so-called double Composite flowers. The appearance of doubling 
is caused in these plants by a mere alteration of the florets of 
their disk into the form of florets of the raj; a very different 
thing from double flowers. (83.) 



316 APPLICATION OF PRINCIPLES. 

exchanged for petals, or in which the number of the 
latter is augmented without any disturbance of the 
former ; in other words, it is a case of the loss, on the 
part of a plant, of the power necessary to develope its 
leaves in the state of sexual organs (83, 84). But 
what causes that loss of power we do not know. It 
can hardly be a want of sufficient food in the soil ; 
for double flowers (the Narcissus, for instance) be- 
come single in very poor soil. On the other hand, it 
can scarcely be excessive vigour ; for no one has ever 
yet obtained a double flower by promoting the health 
or energy of a species. When plants are excessively 
stimulated by unusually warm damp weather at the 
period of flowering, their flowers in such cases some- 
times became monstrous : but the effect of this is to 
lengthen their axis of growth, and to form true leaves 
instead of floral organs (84, fig. 14), just the reverse 
of what occurs in a truly double flower ; the varieties 
of Rosa gallica often exhibit this kind of change. In 
damp cloudy summers, some flowers assume the ap- 
pearance of being double, by the change of their 
sexual organs into small green leaves, as occurred 
very generally to Potentilla nepalensis in the summer 
of 1839, a representation of which is given at page 
61 ; but there was, at the same time, scarcely a trace 
of any tendency, on the part of those leaves, to assume 
the colour or texture of petals. 

• There is, evidently, a greater tendency in some 
flowers to become double than in others, and especial- 
ly in those having great numbers of stamens or pistils. 
All our favourite double flowers, Hepaticas, Paeonies, 



OF THE IMPROVEMENT OF RACES. 317 

Camellias, Anemones, Roses, Cherries, Plums, Ranun- 
culuses, belong to this class ; and, in proportion as 
the natural number of stamens diminishes, so do both 
the disposition to become double, and the beauty of 
the flowers when altered. The Pink and Carnation 
with ten stamens are the handsomest race next to 
those just mentioned ; while the Hyacinth, the Tulip, 
the Stock, and the "Wallflower with six stamens, and 
the Auricula and Polyanthus with five, form altoge- 
ther an inferior race, if symmetry of form, and regu- 
larity of arrangement in the parts of the flower, are 
regarded as beauties of the highest order. If the 
mere circumstance of a plant having but a small num- 
ber of stamens be a bar to its beauty when made 
double, how much greater an obstacle to it must be 
the natural production of unsymmetrical flowers. 
This occurs in the Snapdragon, which, with a 
five-lobed corolla, has but four stamens ; and the 
consequence is, that, when it becomes double, the 
flower is a confused crowd of crumpled petals issuing 
from the original corolla. 

I have heard of attempts to produce double flowers 
by artificial processes, but I never heard of the 
smallest success attending such cases, unless the ten- 
dency to their production had already manifested 
itself naturally ; as in the Stock, which will frequent- 
ly become single from having been double, in which 
case its original double character may be recovered. 
A mode of effecting this has been described by Mr. 
James Munro {Gard. Mag., xiv. 121). Having a 
number of Single Scarlet Ten-week Stocks, he de- 



318 APPLICATION OF PRINCIPLES. 

prived them of all their flowers as soon as he found 
that five or six seed-vessels were formed upon each 
spike, by which means he compelled all the nutritive 
matter that would have been expended upon the 
whole flower-spike and its numerous seed-vessels to be 
concentrated in the small number which he left ; and 
the result, he says, was, that from the seed thus saved 
he had more than 400 Double Stocks in one small bed. 
There can, 1 think, be no doubt that, if any original 
change to a double flower can possibly be effected by 
art, it will be more likely to occur with respect to 
those species which have an indefinite number of 
stamens, where the tendency to this monstrosity al- 
ready exists. It is not many years since the Chryseis 
(Eschscholtzia) Californica, a polyandrous plant, was 
introduced to our gardens ; and I, at one time, made 
some attempts to render it double, conceiving it a 
good subject for experiment on that account, but 
I had no success ; it has, however, accidentally be- 
come semi-double in Mrs. Marryat's garden, at Wim- 
bledon ; and I entertain no doubt that seed skilfully 
saved from that plant would present its flowers in a 
still more double condition. 



CHAPTEE XIX. 

OF RESTING. 

A gardener is said to rest a plant when he ex- 
poses it to a condition in which it cannot grow, and 



OF RESTING. 319 

which is analogous to its winter state. For many 
parts of gardening, especially what relates to forcing 
and the management of exotic plants, this is a subject 
of the first importance. 

If we look over the different climates of the world, 
we shall find that in each there are a season of growth, 
and a season in which, vegetation is more or less sus- 
pended ; and that these periodically alternate, with 
the same regularity as our summer and winter. I do 
not know that there is ir nature any exception to this 
rule: for, even in the Tierra templada of Mexico, 
where it is said that, at the height of 4000 to 5000 
feet, there constantly reigns the genial climate of 
spring, which does not vary more than 8° or 9°, in- 
tense heat and excessive cold being alike unknown, 
and the mean temperature varying from 68° to 70°, 
we cannot suppose that, even in that favoured region, 
a season of repose is wanting ; for it is difficult to con- 
ceive how plants can exist, any more than animals, in 
a state of incessant excitement Indeed, it is pretty 
evident that these countries have a period when vege- 
tation ceases ; for Xalapa belongs to the Tierra tem- 
plada, and we know that the Ipomcea purga, an inha- 
bitant of its woods, dies down annually like our own 
ConvolvulL 

But, although all plants have naturally a season 
of repose, their winter is not in all cases cold. In the 
tropics it is marked by coolness and dryness, while 
the summer is rainy and very hot ; and in extra- tro- 
pical countries the two seasons vary in their charac- 
ter, according to latitude and local circumstances. 



320 APPLICATION OF PRINCIPLES. 

In some parts of Persia, Armenia, and Mesopo- 
tamia, the summer heats are excessive, while the win- 
ters are rendered cold by the proximity of moun- 
tains. Bagdad is described as having a cold winter, 
because of the proximity of the mountains of Koor- 
distan ; yet its heats are intense : in August, 1819, 
the thermometer stood at 120° in the coldest parts 
of the house, and at 108° at midnight in the open 
air. This was preceded by heavy rains, which raised 
the Euphrates 7h feet above the ordinary level : the 
whole country was like a vapour bath, and multi- 
tudes of persons dropped down dead : twenty-two in 
three days in a single caravan. In the northern pro- 
vinces of Mexico the winters are of German rigour, 
while the summers are those of Naples and Sicily 
the Tierra fria of that country has, however, a very 
different climate, the mean heat of the summer being 
76 3 , and the winters so mild that the thermometer 
only occasionally falls below 32°. 

At the Cape of Good Hope there are districts 
in which the period of wet is long and very severe ; 
and many of the favourite flowers of our gardens are 
produced by those districts. The Karroos are plains 
of great extent, destitute of running water, with a soil 
of clay and sand, coloured like yellow ochre by the 
presence of iron, and lying on the solid rock. Dur- 
ing the dry season the rays of the sun reduce the 
soil nearly to the hardness of brick ; Fig Marigolds, 
Stapelias, and other fleshy plants, alone remain green ; 
nevertheless, the bulbs and tribes of Iridaceous and 
other plants are able to survive beneath the sun- 



OF RESTING. 321 

scorched crust, which appears indeed to be necessary 
to their nature. But in the wet season these bulbs 
are gradually reached by the rain ; they swell beneath 
the earth ; and at last develope themselves so simulta- 
neously that the arid plains become at once the seat 
of a charming verdure. Presently afterwards, myriads 
of the gay flowers of the Iridaceae and Mesembryan- 
themums display their brilliant colours ; but in a few 
weeks the verdure fades, the flowers disappear, hard 
dry stalks alone remain; the hot sun of August, 
when in those latitudes the days begin to lengthen, 
completes the destruction of the few stragglers that 
are left, the Karroo again sinks into aridity and deso- 
lation, and the desert reappears. What succulents 
survive are covered with a grey crust, and derive 
their nourishment only from the air. In other parts 
of the Cape of Good Hope the mean range of the 
thermometer in winter is 48° to 93°, with cold rain, 
while that of the summer is from 55° to 96°, with 
dry days and damp nights. 

In the Canaries we have the season of growth from 
November to March, when rains fall like those of 
Europe, and the mean temperature is 66°; and the 
period of rest is April to October, when it never 
rains, and the mean temperature is 73°. 

In Brazil the seasons are thus described by Mr. 
Caldcleugh : — •" The summer begins about the months 
of October or November, and lasts until March or 
April. This is the wet season : but the rains by no 
means descend from morning till night, as in some 
other tropical countries, but commence, generally, 
14* 



322 APPLICATION OF PRINCIPLES. 

every afternoon about four or five o'clock with a 
thunderstorm. The heaviness of the rain can only 
be conceived by those who have been in these lati- 
tudes. This fall naturally arrests the sea breeze, and 
the succeeding night is dark and cloudy. Formerly 
these diurnal rains came on with such regularity that 
it was usual, in forming parties of pleasure, to arrange 
whether they should take place before or after the 
storm. During this period of the year there is sel- 
dom, if ever, a deposition of dew. From April until 
September very little rain falls ; vegetation almost 
stops, and, to the eye of every one who has not just 
arrived from Europe, a wintry appearance is discern- 
ible. The land and sea breezes do not succeed each 
other with the same regularity, and are, besides, 
more frequently disturbed by violent gusts from the 
S. w., imagined to be the tails of those destructive 
winds, the Pamperos of the Kiver Plate. The nights 
are beautifully clear ; Yenus casts a shadow, and the 
southern constellations are seen in all their beauty. 
The dews, as might be expected, are at this season 
very copious." (Brandes Journal, No. 27, p. 41.) 

In other parts of the tropics the seasons of growth 
and rest are equally marked. In Ava, during the 
rainy season, which lasts from May to October, the 
mean temperature varies from 78° to 91 '5° ; while, 
in the dry season, from November to April, it falls to 
from 63° to 80°. At Calcutta, in the growing season, 
from April to October, 58 inches of rain commonly 
fall, with a mean temperature of 79° to 86° ; while, 
during the season of rest, from November to March, 



OF RESTING. 323 

there is not perhaps above an inch of rain, and the 
thermometer sinks to from 66° to 80°. At this 
time vegetation is said, in such countries, to " labour 
under a deadly languor ; but one night's rain con- 
verts an arid plain into a verdant meadow." 

In most of the West India Islands situated under 
the tropic of Cancer, there is said not to be much dif- 
ference in the climate, so that accurate observations 
made on any one of them may be applied with little 
variation to them all. Malte Brun gives the follow- 
ing sketch of their seasons. u The spring begins 
about the month of May ; the savannas then change 
their russet hue, and the trees are adorned with 
a verdant foliage. The periodical rains from the 
south may at this time be expected ; they fall gene- 
rally about noon, and occasion a rapid and luxuriant 
vegetation. The thermometer varies considerably ; 
it falls sometimes six or eight degrees after the diur- 
nal rains ; but its medium height may be stated at 
78° Fahrenheit. After these showers have continued 
for a short period, the tropical summer appears in all 
its splendour. Clouds are seldom seen in the sky ; 
the heat of the sun is only rendered supportable 
by the sea breeze, which blows regularly from the 
south-east during the greater part of the day. The 
nights are calm and serene ; the moon shines more 
brightly than in Europe, and emits alight that ena- 
bles man to read the smallest print ; its absence is in 
some degree compensated by the planets, and, above 
all, by the luminous effulgence of the galaxy. From 
the middle of August to the end of September, the 



324 APPLICATION OF PRINCIPLES. 

thermometer rises frequently above 90°, the refresh- 
ing sea breeze is then interrupted, and frequent calms 
announce the approach of the great periodical rains. 
Fiery clouds are seen in the atmosphere, and the 
mountains appear less distant to the spectator than at 
other seasons of the year. The rain falls in torrents 
about the beginning of October, the rivers overflow 
their banks, and a great portion of the low grounds is 
submerged. The rain that fell in Barbadoes in the 
year 1754 is said to have exceeded 87 inches. The 
moisture of the atmosphere is so great, that iron and 
other metals easily oxidated are covered with rust. 
This humidity continues under a burning sun ; the 
inhabitants (say some writers) live in a vapour bath." 
(Malte Brurfs Geography, vol. v. p. 569, Engl, ed.) 

It is evident, from what has been said, that the 
natural resting of plants from growth is a most 
important phenomenon, of universal occurrence, and 
that it takes place equally in the hottest and the 
coldest regions. It is, therefore, a condition neces- 
sary to the well-being of a plant, not to be overlooked 
under any circumstances whatever ; and there cannot 
be any really good gardening where this is not at- 
tended to in the management of plants under glass. 
Rest is effected in one of two ways ; either by a very 
considerable lowering of temperature, or by a degree 
of dryness under which vegetation cannot be sustained. 

The way in which the physical powers of vegeta- 
tion are affected by this has been already explained 
(114) ; and, in practice, it is found a point of the utmost 
consequence. The early fruit-gardener draws his 



OF RESTING. 325 

Vines out of the vinery, and takes the sashes from his 
Peach and other forcing-houses, when the artificial sea- 
son of growth is over, in order to prepare them for the 
duty of a succeeding season ; although this operation 
is performed in summer, its effect is to expose them 
to dryness, which arrests their growth, and favours 
the deposit in their wood of the matter required for 
the produce of a succeeding year. 

The effects of a very dry atmosphere are necessa- 
rily an inspissated state of the sap of the plant ; and 
this in all cases leads to the formation of blossom 
buds and of fruit. It thus operated upon some 
Pine-apple plants in Mr. Knight's garden, to such an 
extent as to cause even the suckers from their roots 
to rise from the soil with an embryo pine- apple upon 
the head of each, and every plant to show fruit, in a 
very short time, whatever were its state and age. 
Very low temperature, under the influence of much 
light, by retarding and diminishing the expenditure 
of sap in the growth of plants, comparatively with its 
creation, produces nearly similar effects, and causes 
an early appearance of fruit. 

The operations of forcing are essentially influenced 
by these facts ; and, by a skilful alteration of the 
periods of rest, we are enabled to break in upon the 
natural habits of plants, and to invert them so com- 
pletely, that the flowers and fruits of summer are 
obtained to load our tables even in winter. Of this, 
the following instance, taken from a paper by Mr. 
Knight, in the Horticultural Transactions (vi. 232), is 
a sufficient illustration. 



326 APPLICATION OF PRINCIPLES. 

" A Verdelho Vine, growing in a pot, was placed 
in the stove early in the spring of 1823, where its 
wood became perfectly mature in August. It was 
then taken from the stove and placed under a north 
wall, where it remained till the end of November, 
when it was replaced in the stove ; and it ripened its 
fruit early in the following spring. In May it was 
again transferred to a north wall, where it remained 
in a quiescent state till the end of August. It then 
vegetated strongly, and showed abundant blossom, 
which, upon being transferred to the stove, set very 
freely; and the fruit, having been subjected to the 
influence of very high temperature, ripened early in 
the month of February." 

The strawberries of February and March are in like 
manner procured by exposing the plants to such an 
amount of dryness and heat as can be obtained by 
presenting them un watered, in pots, to the sun, at an 
early period of summer ; so as to cause a sufficient 
accumulation of excitability by the end of autumn, 
instead of the month of May. 

It must be manifest that the operations of the flower- 
gardener should be regulated by the same principles, 
although it must be confessed that they are often 
little considered ; a circumstance the more strange, 
from the indispensable necessity of resting fruit 
trees being universally known. It is to the giving 
their plants the proper kind of rest that some gar- 
deners owe the magnificent blossoming of their 
Chinese Azaleas, Cacti, Camellias, and other forced 
flowers, much more than to any peculiarity in the com- 



OF RESTING. 327 

post they employ, which is often a point of subordi- 
nate interest, although generally regarded as of the 
first importance. If but little progress has yet been 
made by art in altering the time of flowering of parti- 
cular races, so as to invert their seasons, this is cer- 
tainly very far from being beyond the reach of attain- 
ment ; and there is apparently no more reason why a 
Chinese Chrysanthemum should not be compelled to 
flower at midsummer instead of November, or a 
Dahlia at Christmas, than that Yines and Strawberries 
should ripen fruit in February. The great difficulty 
to contend against in obtaining winter flowers is want 
of light ; but, by the employment of slender iron sash- 
bars and large glass, a sufficient amount of this im- 
portant vital agent may be obtained in England even 
at that season of the year. 

But it is not merely the periodical rest of winter and 
summer that plants require ; they have also their 
diurnal repose : night and its accompanying refresh- 
ment are as necessary to them as to animals. In all 
nature the temperature of night falls below that of 
day, and thus one cause of vital excitement is dimi- 
nished ; perspiration is stopped, and the plant parts 
with none of its aqueous particles, although it con- 
tinues to imbibe them by all its green surface as well 
as by its roots ; the processes of assimilation are sus- 
pended ; no digestion of food and conversion of it 
into organised matter takes place ; and, instead of 
decomposing carbonic acid by the extrication of oxy- 
gen, they part with carbonic acid, and rob the air of 
its oxygen, thus deteriorating the air at night, al* 



6ZiS APPLICATION OF PRINCIPLES. 

though not to the same amount as they purify it dur- 
ing the day. It is, therefore, most important that the 
temperature of glass houses should, under all circum- 
stances whatever, be lower than that of the day ; and 
it is probable that this ought to take place to a greater 
extent than is generally imagined by even the best 
practical gardeners. We are told that, in Jamaica 
and other mountainous islands of the West Indies, 
the air upon the .mountains becomes, soon after sun- 
set, chilled and condensed, and, in consequence of its 
superior gravity, descends and displaces the warm air 
of the valleys ; yet the sugar-canes are so far from be- 
ing injured by this decrease of temperature, that the 
sugars of Jamaica take a higher price in the market 
than those of the less elevated islands, of which the 
temperature of the day and night is subject to much 
less alteration. At Fattehpur, in the East Indies, the 
difference in temperature between night and day 
amounts to as much as 78°, on an average of the 
whole year ; in April s the greatest heat by day is 110°, 
that of night is only 65° ; in January the thermometer 
falls to 38° at night, while the day is 76' ; and there 
are 40 degrees of difference between the day and night 
in May, one of the hottest months, when the thermo- 
meter ranges as high as 115°. At Calcutta, in May, 
the thermometer averages 93° in the day, and 79° at 
sunrise ; while in January the temperatures are 77° 
and 56° respectively, for those two periods. 

When we compare these facts with the habits of 
plants just adverted to, we must, I think, see that it 
is the purpose of nature to reduce the force which 



OF RESTING. 329 

operates upon the excitability of vegetation at that 
period of twenty -four hours, when, from other causes, 
the powers of digestion and assimilation are suspend- 
ed. As far as is at present known, that power is 
heat ; and therefore we must suppose that, to main- 
tain at night in our hot-houses a temperature at all 
equal to that of the day, is a practice to be much con- 
demned. Plants will no doubt lengthen very fast at 
night in a damp heat, but what is at this time produced 
seems to be a mere extension of the tissue formed 
during the day, and not the addition of any new part ; 
the spaces between the leaves are increased, and the 
plant becomes what is technically and very correctly 
called drawn ; for, as has been justly observed, " the 
same quantity only of material is extended to a greater 
length, as in the elongation of a wire." 

Mr. Knight has pointed out another ill effect of 
high temperature during the night, namely, that it 
exhausts the excitability of a tree much more rapidly 
than it promotes its growth, or accelerates the matu- 
rity of its fruit ; which is, in consequence, ill supplied 
with nutriment at the period of its ripening, when 
most nutriment is probably wanted. The muscat of 
Alexandria, and other late grapes, are, owing as he 
thinks to this cause, often seen to wither upon the 
branch in a very imperfect state of maturity ; and 
the want of richness and flavour in other forced fruits 
is often attributable to the same cause. "There are 
few peach-houses," he adds, "or indeed forcing-houses 
of any kind, in this country, in which the tempera- 
ture does not exceed, during the night, in the months 



330 APPLICATION OF PRINCIPLES. 

of April and May, very greatly that of the warmest 
valley in Jamaica in the hottest period of the year. 
There are probably as few forcing-houses in which 
the trees are not more strongly stimulated by the 
close and damp air of the night, than by the tempera- 
ture of the dry air of the noon of the following day. 
The practice which occasions this cannot be right : it 
is in direct opposition to nature." In the same paper 
from which the foregoing is an extract (Hort. Trans., 
ii. 135), the same great experimentalist records the 
result of his own management of a peach-house, where 
a due regard was had to the preservation of a suffi- 
ciently low temperature at night. " As early in the 
spring as I wanted the blossoms of my Peach trees to 
unfold, my house was made warm during the middle 
of the day ; but towards night it was suffered to cool, 
and the trees were then sprinkled, by means of a large 
syringe, with clear water, as nearly at the tempera- 
ture at which that usually rises from the ground, as 
I could obtain it ; and little or no artificial heat was 
given during the night, unless there appeared a pros- 
pect of frost. Under this mode of treatment, the 
blossoms advanced with very great vigour, and as 
rapidly as I wished them, and presented, when ex- 
panded, a larger size than I had ever before seen of 
the same varieties ; which circumstance is not unim- 
portant, because the size of the blossom, in any given 
variety, regulates, to a very considerable extent, the 
bulk of the future fruit." 



OF SOIL AND MANURE. 331 

CHAPTEE XX. 
OF SOIL AND MANURE. 

Notwithstanding all that has been written upon 
these substances, and the endless accounts we possess 
of their real or supposed action upon vegetation, I 
must confess that the contradictions are so numerous, 
the exceptions to supposed rules so frequent, and phy- 
siology is so insufficient to account for the greater 
number of well ascertained facts, that it does not 
appear to me possible to construct any tolerable 
theory relating to them.* 

Mr. Knight has observed that varieties of the same 
species of fruit tree do not succeed equally in the 
same soil, or with the same manure : the Peach in 
many soils acquires a high degree of perfection, 
where its variety, the Nectarine, is of comparatively 
little value ; and the Nectarine frequently possesses 
its full flavour in a soil which does not well suit the 
Peach. The same remark is also applicable to the 
Pear and the Apple ; and, as defects of opposite 
kinds occur in the varieties of every species of fruit, 
those qualities in the soil which are beneficial in some 
cases will be found injurious in others. In those dis- 

[* These remarks were perfectly applicable when this work was 
published (early in 1840) ; but the treatise on Organic Chemistry in 
its applications to Agriculture and Physiology, by the distinguished 
Professor Liebig, which appeared a few months later, has greatly 
elucidated the whole subject.] 



332 APPLICATION OF PRINCIPLES. 

tricts where the Apple and Pear are cultivated for 
cider and perry, much of the success of the planter 
is found to depend on his skill or good fortune in 
adapting his fruits to the soil. (Hort. Trans., i. 6.) 
Rhododendrons and Kalmias are usually cultivated 
in peat earth mixed with sand, and yet they grow as 
well in fresh hazelly loam, without any mixture 
whatever; and, than these two kinds of soil, none 
can be apparently more dissimilar. The fine Ame- 
rican cottons are grown in a calcareous sand, those 
of India in deep black saponaceous earth : the Ame- 
rican cotton will not thrive in the latter, nor that of 
India in the former, as has now been ascertained; 
and yet the species of Gossypium producing the two 
qualities have no organic differences which can, so 
far as has yet been ascertained, explain in the smallest 
degree the necessity, under which it is evident that 
they labour, of being provided with different kinds 
of food. The Alnus glutinosa, or Common Alder, 
flourishes in wet clayey meadows ; while Alnus 
incana, or Upland Alder, is equally suited to a dry 
and high land : we are totally ignorant of the reason 
of such a case as this. Rhododendron hirsutum and 
Erica carnea are, in their wild state, confined to cal- 
careous soil ; while Rhododendron ferrugineum grows 
exclusively on granite, and Erica vagans on serpen- 
tine. We are informed by Bey rich {Gardener's 
Magazine, iii. 442) that " the Pine-apple, in its wild 
state, is found near the sea-shore ; the sand accumu- 
lated there in downs serving for its growth, as well 
as for that of most of the species of the same family. 



OF SOIL AND MANURE. 333 

The place where the best Pine-apples are cultivated 
is of a similar nature. In the sandy plains of Praya 
Yelha and Praya Grande, formed by the receding of 
the sea, and in which no other plant will thrive, are 
the spots where the Pine-apple grows best. The 
cause of this lies evidently in the composition of the 
sand, which chiefly consists of salt, lime from decom- 
posed shells, and a very little vegetable mould. 
Warmth, lime, salt, and moisture, seem therefore 
to be the principal ingredient in which the Pine-apple 
thrives. Sand will take a very high and continued 
degree of warmth, being often heated by the sun so 
much as to scorch vegetation, and yet it seldom dries 
to a greater depth than from eight inches to one foot. 
Sea salt is well known for its property of attracting 
the nocturnal damps, and retaining them a long 
time. The lime of the shells seems to be the princi- 
pal manure, which has also been proved by the Eng- 
lish here, who, by manuring their Pine -apples with a 
mixture of stamped oyster-shells and vegetable earth, 
produce very large fruit. The natural mould, usually 
slightly mixed with sand, is partly of a vegetable, 
and partly of a mineral origin." But it is well known 
that the Pine-apples of England are much superior to 
those of South America, and yet English gardeners 
grow their plants neither in sand ; nor saline nor cal- 
careous soil. As to manures, some plants bear them 
in almost any quantity, others suffer from the access 
of only a small quantity. The Yine and the Mul- 
berry can hardly be over-manured, no soil was ever 
found too rich for Roses : but Coniferous plants can 



334 APPLICATION OF PRINCIPLES. 

scarcely bear any manure, and the Peach is often 
greatly injured by excess of it in a solid state : yet 
this same plant will bear a very considerable quantity 
in a liquid form. 

The application of soils and manures to plants must, 
therefore, remain at present exclusively within the 
domain of art. There are, however, some general 
remarks which it is possible to offer with tolerable 
confidence. 

Soil, considered without reference to the organisable 
substances it contains, appears to act upon plants 
chiefly by its power of absorbing and parting with 
heat and moisture. When soil is tenacious, or plastic, 
it absorbs heat slowly, and it parts with its water with 
great difficulty, as is the case in the London clay ; 
the number of cultivated plants to which this is suit- 
able is so small that it is almost expelled from gar- 
dens, where the object is to expose the cultivated 
species to conditions more favourable than those 
afforded them by nature. The small amount of bot- 
tom heat afforded by clay, and the impossibility of 
effectually draining it, sufficiently explain the badness 
of its quality for gardening purposes, even without 
taking into account the difficulty experienced by 
plants in rooting in it, from the resistance afforded to 
the passage of the spongioles by so compact a sub- 
stance. On the other hand, loose sand, whose par- 
ticles have no cohesion, although it imbibes water with 
great facility, parts with it as readily, and, being easily 
heated by the sun's rays, becomes so soon dried up 
as to be for that reason as unsuitable to most plants 



OF SOIL AND MANURE. 335 

as plastic clay itself. It is by obtaining a mean be- 
tween these two extreme cases that the soil is formed 
most favourable to the growth of plants in general ; 
hence the mixtures of peat, loam, and sand, which 
are so continually employed. These substances 
counteract each other's influences, the loam by conso- 
lidating the sand, and the sand by lightening the 
loam, and the peat by binding them all together, and 
preserving their perfect admixture, independently of 
its manuring qualities. It is, however, a well ascer- 
tained fact, that loam containing a considerable quan- 
tity of calcareous matter is in general much better 
suited to cultivation than such as is destitute of it : 
the reason for which seems to be, in part, that calcare- 
ous earth enters largely into the organisation of all 
plants, in which it is deposited in the state of the 
oxalate and phosphate of lime ; and, in part, because, 
as was shown by Davy, there is a strong action be- 
tween the lime and vegetable matter contained in 
soils, the result of which is a compost partly soluble 
in water.* 

* [The extensive beds of marl distributed over a considerable 
portion of this country are just coming into use, and will ultimately 
prove valuable in the highest degree to the cultivator. W~e have 
found this substance peculiarly adapted to promote the growth and 
productiveness of the Peach and the Vine. In New Jersey, thou- 
sands of acres of sandy soil formerly sterile and worthless have been 
rendered fertile and productive by the application of marl. In other 
districts it is now used to a considerable extent for top-dressing 
grass-land, corn fields, <fcc. From ten to forty loads per acre, ac- 
cording to the quantity of calcareous matter contained, are generally 
applied. A. J. D.] 

[It is easy to understand the rationale of the favourable effects 



336 APPLICATION OF PRINCIPLES. 

Doubtless one of the safest rules for a gardener, in 
determining the soil required for a given plant, would 
be, if practicable, to ascertain what amount of mineral 
matters it contains, and to select earth in which those 
substances abound. For, although it may be asserted 
that the presence of iron, copper, or other substances, 
in plants, in minute quantities, is accidental and un- 
important, yet such a supposition is gratuitous, if not 
altogether unfounded ; for I do not know what war- 
rant we have for saying that any of the constant 
phenomena of nature, however minute they may seem 
to be, are accidental. This at least is certain, that, 
where mineral substances occur abundant]}' in plants, 
they are part and parcel of their nature, just as much 
as iron and phosphate of lime are of our own bodies ; 
and we must no more suppose that grasses can dis- 
pense with silica in their food, or marine plants with 
common salt, than that we ourselves could dispense 
with vegetable and animal food. Flint is found on 
the exterior of the whole Graminaceous order, with- 
out exception ; it forms the polished surface of the 
Cane Palm, the grittiness of many kinds of timber ; 
sulphur abounds in Cruciferous plants, especially 

of the Xew Jersey marl, when we consider its chemical composition. 
According to the numerous analyses of Mr. Rogers, the marl from 
various localities contains from 9 to nearly 13 per cent, of potash, 
and seldom more than one-half per cent, of lime: and Mr. Rogers* 
very correctly states " that the true fertilising principle in marl is 
not lime but potash." On this subject see the note commencing on 
p. 337. G.] 

* Final Report on the Geology of the State of New Jersey; by Hear}' D. Rogers, 
1840. 



OF SOIL AND MANURE. 337 

Mustard ; copper in Coffee,* Wheat, and many other 
plants (it is believed in the state of a phosphate) ; 
iron, as a peroxide, in Tobacco. John, in his experi- 
ments upon these matters, found that the Ramalina 
fraxinea and Borrera ciliaris, two lichens, contained 
a great quantity of the last metal, although he could 
not find a trace of it in the Fir tree, on the topmost 
branches of which the lichens grew. We cannot sup- 
pose that such things are the result of accident, and 
that it is unimportant to the plants containing mine- 
rals thus constantly, whether such substances are pre- 
sent in their soil or not.f 

* Seventy millions of kilogrammes of coffee arrive annually in 
Europe ; of these, 560 kilogrammes consist of copper, according to M. 
Sarzeau. The weight of copper consumed in bread in France is 3650 
kilogrammes annually. (De Candolle, Physiologie Vegetale, p. 389.) 

f [The quantity of earthy or saline matters which different plants 
absorb is probably nearly uniform, under the same circumstances, 
since their roots possess little if any power of selection. But the 
quantities which are retained vary according to the constitution of 
each species, and the chemical composition of its producta The 
ashes of Pine and Fir trees, no matter on what soil they may have 
grown, contain a much smaller quantity of alkalies than the ashes 
of the Oak, Beech, or Maple. Hence the former are found to thrive 
upon sandy or sterile soils, which do not furnish sufficient alkali for 
the latter. All plants of the grass kind require a considerable por- 
tion of silicate of potash, which is deposited in their stems ; and of 
phosphate of magnesia, which is a constituent of their seeds. The 
quantity of both varies in different species. " One hundred parts of 
the stalks of Wheat yield 15 -5 parts of ashes ; the same quantity of 
the dry stalks of Barley 8 '54 parts; and one hundred parts of the 
stalks of Oats only 4*42 ; the ashes of all these are of the same com- 
position. " These several crops, therefore, extract the potash of the 
soil in different degrees ; and upon a field which will yield but one 
harvest of Wheat, two crops of Barley or three of Oats may be 

15 



338 APPLICATION OF PRINCIPLES. 

Manures act apparently in one of three ways, 
either by merely stimulating the vital forces, as corn- 
raised. Peas, and many other leguminous plants, take very little 
alkaline or earthy matter from the soil : they contain no potash, 
and only a trace of phosphate of lime or magnesia. This explains 
their utility as fallow-crops: they return to the soil a certain portion 
of vegetable mould, while they scarcely if at all diminish the potash 
or the phosphates of the soil, which are required for the succeeding 
wheat crop. " When we grow in the same soil, for several years in 
succession, different plants, the first of which leaves behind that 
which the second, and the second that which the third, may require, 
the soil will be a fruitful one for all the three kinds of produce. If 
the first plant, for example, be Wheat, which consumes the greatest 
part of the silicate of potash in a soil, while the plants which suc- 
ceed it are of such a kind as require only small quantities of potash, 
as is the case with the Leguminosce [Pea tribe], Turnips, Potatoes, 
<fcc, the wheat may be again sowed with advantage after the fourth 
year; for, during the interval of three years, the soil will be render- 
ed capable of again yielding silicate of potash in sufficient quantity." 
(Liebig, Organic Chemistry, p. 170.) The alkaline constituents of 
the soil, except when added in the form of manure, are derived from 
the slow disintegration and decomposition of the rocks which com- 
pose it, and particularly the argillaceous earths. According to 
Liebig, the quantity of potash contained in a layer of soil formed by 
the disintegration of 40,000 square feet of the following rocks to the 
depth of 20 inches, is as follows ; 

Felspar contains 1,152,000 lbs. 

Clinkstone contains from 200,000 to 400,000 lbs. 

Basalt contains from 47,500 to 75,000 lbs. 

Clay-slate contains from 100,000 to 200,000 lbs. 

Loam contains from 87,000 to 300,000 lbs. 

" A thousandth part of loam, mixed with the quartz in new red 
sandstone, or with the lime in the different limestone formations, 
affords as much potash to a soil only 20 inches in depth as is sufficient 
to supply a forest of pines growing \ipon it for a century. A single 
cubic foot of felspar is sufficient to supply a wood, covering a surface 
-of 400,000 square feet, with the potash required for five years." 



OF SOIL AND MANURE. 839 

mon salt ; or by their power of absorbing moisture 
from the atmosphere, as salt and the muriate of lime, 

(Liebig, op. cit. p. 145.) "A soil which has been exposed for cen- 
turies to all the influences which effect the disintegration of rocks, 
but from which the alkalies have not been removed, will be able to 
afford the means of nourishment to those vegetables which require 
alkalies for their growth during many years ; but it must gradually 
become exhausted, unless those alkalies which have been removed 
are again replaced : a period therefore will arrive when it will be 
necessary to expose it, from time to time, to a further disintegration, 
in order to obtain a new supply of soluble alkalies. For small as is 
the quantity of alkali which plants require, it is nevertheless quite 
indispensable for their perfect developement. But when one or more 
years have elapsed without any alkalies having been extracted from 
the soil, a new harvest may be expected. The first colonists of Vir- 
ginia found a country, the soil of which was similar to that mention- 
ed above ; harvests of Wheat and Tobacco were obtained for a cen- 
tury from one and the same field, without the aid of manure ; but 
now whole districts are converted into unfruitful pasture land, which 
without manure produces neither Wheat nor Tobacco. From every 
acre of this land there were removed, in the space of 100 years, 1200 
lbs. of alkalies in leaves, grain, and straw ; it became unfruitful, 
therefore, because it was deprived of every particle of alkali which 
had been reduced to a soluble state, and because that which was 
rendered soluble again in the space of one year was not sufficient to 
satisfy the demands of the plants. ... It is the greatest possible 
mistake to suppose that the temporary diminution of fertility in a 
soil is owing to the loss of humus [vegetable mould] ; it is the mere 
consequence of the exhaustion of the alkalies." {Op. cit. p. 148.) 
This proposition is very perfectly made out by this distinguished 
organic chemist ; and the true theory of the operation of manure ; 
of the interchange of crops, <fec, is thence readily and satisfactorily 
deduced. The limits of a note will not allow us to enter farther into 
the consideration of this subject, so important to agriculture and 
horticulture ; which is the less necessary, now that an American edi- 
tion of the work from which these observations are drawn has been 
announced. G.] 



340 APPLICATION OF PRINCIPLES. 

obtained by mixing toge.her equal parts of salt and 
lime ; or by supplying the plant with soluble carbon 
and nitrogen. It is in proportion to their power of 
furnishing these principles, and to the length of time 
during which they continue to do so, that manures are 
active or sluggish, and durable or ephemeral in their 
operation. Carbonic acid, when decomposed, fur- 
nishes an jessential part of the starch and other sub- 
stances secreted by plants ; and nitrogen seems, from 
its great abundance in their system, at least when 
young, to be indispensable to their existence : the 
first is a fact of universal notoriety, the latter has been 
ascertained by modern chemists to be also apparently 
a constant phenomenon. (See Introduction to Botany, 
3d ed. p. 370, 379, &c, and Appendix.) For these 
reasons every description of putrefying animal or 
vegetable matter, from putrid yeast and malt-dust to 
horses' hoofs and feathers, have been used for the 
purpose of fertilising land, the nature of whose differ- 
ent actions constitutes a study of itself, very obscure, 
but of the highest degree of importance. 

In the more delicate of horticultural operations, 
liquid manure, prepared by steeping dung in water, 
and drawing it off when clear and of the colour of 
porter, is most generally now employed, and is 
undoubtedly the best form in which it can be admi- 
nistered, in consequence of its concentration, the faci- 
lity of its administration in any quantity, and its con- 
taining nothing but soluble matter. It was first used 
by Mr. Knight, who not only applied it with great 
advantage to Fruit trees, but also to the Heaths and 



OF SOIL AND MANURE. 341 

other flowers ; and it is, with the exception of bone 
dust, the form of manure best adapted to all plants 
in pots.* 

What most concerns the subject of this work is, 
not the nature of manure, but the proper time and 
manner of applying it to garden plants. Provided 
manure is of a permanent character, it does not very 
much matter at what time it is administered, because, 
if it does not act at first, it will sooner or later ; but 
when it is of such a nature as to be easily dissipated, 
like malt-dust, or soot, or yeast, a knowledge of the pro- 
per season becomes extremely necessary. Plants will 
not receive the influence of manure so readily at any 
season as when they are in the most rapid and steady 
growth ; because at that time the absorbing force of 
their roots, and their vital energies, are all greatest. 
It is for this reason that a top-dressing is almost use- 
less to a lawn at midsummer, but better in the spring, 
and best of all in October. If applied at midsummer, 
the ground is dry, the herbage closely shorn, and the 
vegetation extremely languid, partly in consequence 
of the constant operation of the mower, and partly 
because our summertide is the winter of herbage 
grasses, which only flourish in the cool and damp 

* The efficacy of liquid manure, applied out of doors, is doubled by 
applying it in damp weather or before rain, when the plants are in 
a growing state. The same remark applies to guano and other con- 
centrated manures that require a large amount of water to make 
them soluble. Hundreds of persons have been entirely disappointed 
in the use of guano, and animal manures generally, because they 
applied thein so late in the spring that they were never rendered 
sufficiently soluble to be taken up by the roots of plants. A. J. D. 



342 APPLICATION OF PRINCIPLES. 

seasons of the year. When a top-dressing is applied 
in the spring, the lawn profits by it so long as it con- 
tinues to grow vigorously ; but the quick approach 
of summer daily interferes with the force of this kind 
of vegetation, and diminishes the effects of the 
manure. On the contrary, if October is the season 
chosen for the operation, the grasses are then begin- 
ning to grow steadily, the operations of the mower 
are, or should be, suspended, and there are seven clear 
months at least during which the effects of the 
manure continue to be felt. 

It may be indifferent at what season such manure 
as bones, and other kinds of matter which decompose 
very slowly, are employed ; yet there can be no 
doubt that upon every known principle they also 
should be given at a time when vegetation is most 
active; hence the every-day practice of digging 
manure into the borders of a garden in spring, or 
shortly before an annual crop is about to be commit- 
ted to the soil. 

As to the manner of applying manure, it must be 
obvious that it can be of no use unless it is in contact 
with the absorbing parts of the roots; now those 
parts are the young fibres and spongioles, as has been 
already stated (23, 24), and, when plants have arrived 
at any considerable size, the roots form the radii of 
a circle whose circumference is the principal line of 
absorption. This being so, if a plant has arrived at 
the state of a bush or tree, it is useless to apply 
manure at the base of the stem, because that is pre- 
cisely where the power of absorption is the weakest, 



OF SOIL AND MANURE. 343 

if it exists at all ; and, as the circle formed by the 
roots is generally greater than that of the branches, 
the proper manner of applying manure is to introduce 
it into the ground at a distance from the stem about 
equal to the radius formed by the branches. And, 
yet, although this is so evidently right, I have seen 
a gardener, who ought to have known much better, 
sedulously administering liquid manure, by pouring 
it into the soil at the base of the stem; which is 
much the same thing as if an attempt were made 
to feed a man through the soles of his feet 



INDEX. 



A. 

Absorption, force of, in spongelets, 16. 

Acetate of lime, solution of, rejected by roots, 18. 

Air, deterioration of, by plants at night, 32*7 — introduction of heated, 
to plant compartments, 153 — purification of, by plants, during 
the day, 328 — of plant-houses, ventilation a means of drying, 153. 

Air passages penetrate plants in all directions, 102. 

Alburnum, 26 — its connexion with the spongelets, 12 — offices per- 
formed by it, 32 — its importance, 33 — its quantity proportionate 
to the number of buds, 187. 

Alburnous substance, 18*7. 

Ammonia employed to promote germination, 166. 

Amylaceous substance, 188. 

Annuals, oleraceous, 114. 

Annual rest of plants, 319. 

Anther, 56. 

Aquatic plants, 114 — necessity of maintaining a due degree of tern 
perature in the water in which they are grown, 109. 

Aqueous matter, necessity of its excess being decomposed in fruits 
during the process of ripening, 115. 

Aqueous particles in plants, effects of their being frozen, 86. 

Arid regions, 321. 

Atmosphere, temperature of, at various places, 100 — unfavourable 
state of, a caxise of sterility in flowers, 1*71 — dry, produces an 
inspissated state of the sap, 325. 

Atmospheric dryness, or moisture, extremes of, 132, 133 — averages 
of, 133 — moisture, 125. 

Axil, 30. 

Axils of leaves, the situation where leaf-buds are formed, 30. 

B. 

Balloon training, 262. 

Bark, 28 — its production, 26 — its distinct parts, in trees and shrubs, 
27 — its anatomical relation to leaves, 37 — of the root, its offices, 

15* 



346 INDEX. 

12 — its absorbent property, 13 — its rind and epidermis in some 
cases perform the office of leaves, 40. 

Bell glasses, their use in propagation by cuttings, 203 — of different 
colours, 205. 

Bleeding, 244 — of vines, preventive against, 245. 

Blossom-buds, their identity with leaf-buds in the first stage of 
organisation, 62. 

Bottom heat, 102 — its effects different from those resulting from 
solar radiation, 93 — its natural amount, 103 — necessary for the 
flowering of many tropical plants, 107 — degree of, communicated 
to plants in pots, from the atmosphere of a stove, 111 — its va- 
riation agreeably to that of the soil of countries, 112. 

Branches, their vigour augmented by the abstraction of flowers and 
fruit, 309 — effects of their being subjected to a widely different 
temperature from that of the roots, 50. 

Budding, propagation by, 210 — mode of operation, 212. 

Buds, the origin of branches, 15 — not the origin of roots, 15 — ad- 
ventitious in roots, 22 — embryo, 30 — their relation to bulbs, 30 — 
latent, 37 — mature, preferable to immature for the purpose of 
propagation, 232 — the youngest most excitable, 232. 

Bulbs, 31, 114 — a species of bud, 37 — in arid regions, 320 — effect of 
scarring their centre, 210. 

C. 

Callus, 26 

Calyx, its situation and colour, 55 — its use, 67. 

Camellias, a method of propagating them, 239. 

Canker, 106. 

Cape heaths, drainage for, 275. 

Capillary tubes give hygrometrical force to tissue, 17. 

Carbon, excess of, in seeds, 8 — its conversion into carbonic acid dur- 
ing the process of germination, 9 — a component of the food of 
plants, 18 — proportions of, in certain vegetable secretions, 76 
— in seeds, 175, 179 — necessary to preserve their vitality, 179 — 
requires its proportion altered before germination can be effect- 
ed, 78. 

Carbonic acid, its formation during the process of germination, 9 — 
its decomposition in plants by solar light,"41 — its mode of in- 
troduction into the system of plants, 41 — its decomposition in 



INDEX, 347 

plants during the day, 42 — its formation by plants during the 
night, 42 — its digestion and decomposition in the system of 
plants, 42 — period at which leaves cease to decompose it, 53 — 
conditions under which it is slowly formed, 16*7 — formation of, 
in seeds, 180 — decomposed, furnishes an essential part of the 
secretions of plants, 840. 

Carburetted hydrogen gas, 118. 

Cellular system, 217 — horizontal, 282. 

Cellular tissue combined with woody fibre, 14, 

Charcoal, packing seeds in, 181. 

Chemical changes in seeds, 1-59, 

Cherries, forcing of, 109. 

Ghinese mode of dwarfing trees, 251 

Chlorine employed to promote germination, 16V. 

Cicatrisation, 282. 

Circulation of sap, 32. 

Climate, uniform, 319. 

Climates, extreme, 320 — extreme, imitation of, 107. 

Climbers, 265. 

Colour of leaves influenced by light, 52 — the natural green in plants, 
circumstances which prevent its being acquired, 34 — green, in 
plants, how produced, 84 — yellow, in plants, cause of its occur- 
rence, 84. 

Colouring matter, green, decomposed by frost, 86. 

Colours of plants, cause of their formation, 84. 

Cormi, 29. 

Corolla, its nature, 55 — its use, 67. 

Cortical integument, 27. 

Cotyledons, 10 — supply nourishment to the plumule, 28. 

Creepers, 265. 

Crops, change of, 270, 338, 339 

Cross-beds, 68 — are generally fertile, 68. 

Cross-breeding, 310 — process of, 314. 

Cucumbers, advantage of growing them in forcing-houses, instead of 
pits, in winter, 155. 

Curl in potatoes, 73. 

Cuttings, propagation by, 195 — conditions required in order to en-^ 
able them to become young plants, 195 — double pots employed 
in striking them, 202. ...:.: 



348 INDEX. 

D. 

Damping off, 149. 

Deciduous plants, 73 — trees, season for transplanting, 282. 

Degeneracy, means of preventing it in seed crops, 802. 

Degeneration of varieties, 302. 

Deleterious matter thrown off by roots, 20 — substances, when 
attenuated, are most likely to prove injurious to plants, 18. 

Dew-point, 126. 

Digestion, a function of the leaves, 40. 

Diurnal rest of plants, 327. 

Drainage, 118 — of pots for plants, 119, 275 — of soil in pots by frag- 
ments of absorbent stone, 275. 

Dryness, atmospheric, table of, with regard to the direction of the 
wind, 133, 134 — causes of, in hothouses, 143. 

Double composite flowers, 315. 

Double Dahlias not truly double flowers, 315. 

Double flowers, 315 — conditions under which they may and may not 
produce seed, 173. 

Double pots employed for striking cuttings, 202 — for plants, 274. 

Double Stocks, 318. 

Dung-heat, Grapes and Nectarines forced by it, 146. 

Dwarfing trees, Chinese mode of, 251. 



Earth, temperature of, at various places, 91, 92. 

Earths, certain of them enter into the composition of the food of 

plants, 17. 
Easterly winds, their dryness, 130. 
Embryo buds, 30. 

Endogens, 24, 29 — mixed arrangement of their tissue, 29. 
Envelopes, not a necessary part of a flower, 55. 
Epidermis, in its young state, highly sensible to the stimulus ol 

light, 115 — regulates the amount of perspiration, 53 — of leaves, 

88 — an extension of the outer bark of the stem, 40 — of the 

leaves of evergreens, 285 — of plants inhabiting shaded situations, 

44. 
Evaporation, an important vital function of plants, 125 — affected by 

elevation, 129— affected by wind, 129— from the surface of 

scions, 235. 



INDEX. 349 

Evergreen plants, 53. 

Evergreens, season for transplanting, 284— epidermis of their leaves, 
285. 

Excitability diminished by lowness of temperature, 87. 

Excrementitious matter of plants poisonous, 20, 21 — matter of plants 
superfluous, 20. 

Excretory functions of roots, 2*70. 

Exogens, 24, 29 — their pith central and distinct, 24, 

Exposure of green-house plants, 2*73. 

Eyes, propagation by, 184. 

F. 

Fall of the leaf, 54. 

Fertilisation, 68 — of the Mistletoe, 314. 

Fibrous roots, production of, by. root-pruning, 292. 

Fibre, woody, originates in the leaves, 24. 

Field crops, germination of, in wet seasons, 1*76. 

Fig-trees, mode of pruning, 242. 

Filament, 55. 

Floral envelopes, 55. 

Flowers, their action, 55 — their structure, 55 — essentially constituted 
only by the presence of the sexes, 56 — double, 57 — their parts 
are modified leaves, 62 — their metamorphoses, 57 — their pro- 
duction induced by ringing, 253 — tendency in some to become 
double, 316 — causes of their not expanding, 84. 

Flower-buds, their production depends upon the presence of nutritious 
matter, 64. 

Flues, 143. 

Fluids, ascending, their channel in plants, 27 — their mode of descent, 
27 — their lateral transmission, 33 — are attracted into the sys- 
tem of plants, during the night, 49. 

Flute-budding, 215. 

Food, natural, of plants, 18. 

Frost, its effects on plants, 84 — its physiological effects on vegetables 
accounted for, 140 — its accumulation in valleys, 138. 

Fructification, period of its commencement in plants, 63 — may be 
advanced or retarded artificially, 64 — means of advancing its 
period, 64 — influenced by ringing, 65 — its removal in a young 
state strengthens the functions of the leaves, 79 — induced by 
an inspissated state of the sap, 325. 



350 INDEX. 

Fruit, its maturation, 69 — its ripening affected by pruning, 246 — ita 
physiological action analogous to that of a leaf, 71 — its physio- 
logical use, 71 — derivation of its food, 70 — is an advanced stage 
of a flower, 69 — differs from leaves in its appropriation of the 
sap which it receives, 73 — attracts food from the surrounding 
parts, 70 — its secretions, 74 — changes which it undergoes, 74 — 
aqueous matter in, requires decomposition, 116 — succulent, 
ripening of, 116 — effects produced on, by ringing, 254 — method 
of obtaining improved varieties of, 311 — superior and inferior, 
table of, 71 — on what its size and excellence depend, 72 — cause 
of the weaker portion of it being generally thrown off, 72 — the 
secretions of, partly changed by heat, 74 — influenced by light, 
74 — the decomposition or dissipation of water by, 76 — the ripen- 
ing of, retarded by an excessive supply of water, 76. 

Functions of leaves, termination of their performance, 57. 

Fungi, deleterious parasitic, 149, 155. 



Garden, choice of soil for a, 137 — situation for a, 137. 

Gases, their destructive effects on vegetation, 152. 

Geothermometrical averages, 94. 

Germination, 7 — conditions required to produce it in seeds, 8 — why 
best effected in the absence of light, 9 — requires communication 
with the atmosphere, 8 — requires different degrees of heat in 
different species, 9 — causes of, 78 — degree of heat required for 
seeds of tropical trees, 103 — is assisted by the absorption of 
water, 8 — interrupted, 160. 

Germination, means of promoting it, 163 — means of assisting it in 
cases of seed with very hard integuments, 164. 

Glass, the coldness of its surface condenses the enclosed atmospheric 
vapour, 114. 

Glass roofs, their coldness a cause of dryness in the state of the in- 
ternal air, 143. 

Glazed houses, means of applying temperature and moisture to the 
atmosphere of, 142. 

Grafting, propagation by, 216 — modes of operation, 216, 219 — de- 
grees of affinity within which the operation maybe performed, 
222 — deceptions practised with regard to it, 223 — on roots, 224 
— herbaceous plants, 236 — pines, 237. 



INDEX. 351 

Grafting clay, its use in preventing evaporation and affording 

aqueous food for the scion, 235. 
Grafting plasters, thei r unfitness to supply aqueous food to scions, 235. 
Grass, its fibrous texture favourable to the emission of heat, 13*7. 
Granulation, 282. 

Granulations of cellular tissue, 235 — formed by the living tissue, 293. 
Grapes, a cause of their shrivelling, 106. 
Greenhouse plants, their exposure, 273. 
Growth by the stem, 22. 
Growing point, 22. 

H. 

Heart-wood, its mode of formation, 27 — the oldest formation, 27. 

Heat, its impulse to the vital principle, 9 — necessary to produce 
germination, 8 — produces a distension of all the organic parts, 9 
— degree of, most conducive to germination, is variable, 9 — its 
agency in changing the secretions of fruits, 74 — the stimulus of 
excitability, 87 — acts as a stimulus to the vital forces, 107. 

Herbaceous grafting, 236. 

Horizontal plane, bad effects of training on a, 257 — system, 214. 

Horizontal cellular system, 282 — systems of stocks and scions, neces- 
sity for their correspondence in growth, 222. 

Hothouses, causes of atmospheric dryness in, 143. 

Hot springs, their effects on surrounding vegetation, 103. 

Hybrids, their origin, 68 — are generally sterile, 69. 

Hydrogen, fixed in the tissue of plants, 8 — excess of, in certain vege- 
table secretions, 75 — incorporated in the tissue of plants, deri- 
vation of its supply, 18. 

Hygrometers, 126 — Daniell's, 126. 

I. 

Improvements in the races of plants by direct means, 807 — by indi- 
rect means, 309. 

Inarching, 238 — circumstances conducive to its success, 239. 

Inner bark, 24. 

Insects, 124 — their ravages on vegetables, preventive of, 124— con- 
ducive to fertilisation, 172. 

Iron roofs for plant-houses, light afforded by, 326. 



352 INDEX. 

K. 
Knaurs, propagation by, 189. 

L. 

Latex, its destruction by frost, 85. 

Layering, Chinese mode of, 209. 

Layers, propagation by, 207. 

Leaf, an expansion of the bark, 37. 

Leaf-buds, their reproductive properties different from that of seeds, 
7 — locality of their formation, 30 — adventitious, 31 — their pro- 
perties, 30 — their formation on stems, 30 — their importance, 32 
— the parents of wood, 30. 

Leaf-buds, their presence universal, either latent or developed, in 
the axils of leaves, 37 — instances of their formation on leaves, 55 
— their identity with blossom-buds in the first stage of organi- 
sation, 62 — on cuttings, 196, 20-4. 

Leaves give origin to woody tissue, 23 — their action, 37 — attraction 
of, causes the flow of sap, 36 — their nature, 37, 41 — their modi- 
fications have leaf-buds in their axils, 37 — have universally 
leaf-buds, either latent or developed in their axils, 37 — their 
epidermis, 38 — number of stomates on the surface of, in various 
species, 39 — particular offices of, 40 — their free action essential 
to the health of plants, 40 — their action reciprocal with that of 
the roots, 49 — their absorption of moisture from the air, 50 — 
their action forms the peculiar secretions of plants, 51 — their 
colour influenced by light, 52 — period at which they cease to 
decompose carbonic acid, 54 — ultimately become incapable of 
performing their functions, 54 — are organs of digestion and 
respiration, 54 — their temporary nature, 54 — instances of leaf- 
buds being formed on them, 55 — modified, constitute the parts 
of flowers, 62 — their physiological action analogous to that of 
the fruit, 71 — their functions strengthened by the early removal 
of the fructification, 75 — propagation by, 189 — conditions most 
favourable for propagation by, 195 — their action forms roots, 
195 — of evergreens, 285. 

Liber, its consistence, 24 — its situation, 26 — the internal part of the 
bark, 26 —offices performed by the, 32 — its importance, 33. 

Ligatures for buds, 215 — objects of their application with regard to 
the fertility of trees, 255. 



INDEX. 353 

Light, detrimental to the germination of seeds, 9 — its absence con- 
ducive to the formation of carbonic acid, 9 — conducive to the 
formation of roots, 14. 

Light, by its action on the leaves a principal agent in forming secre- 
tions, 52 — its effect on the colour of leaves, 52 — its agency in 
changing the secretion of fruits, 74 — its stimulating effects, 115 
— its effect in altering and decomposing the fluids of plants, 115 
— an abundance of, with low temperature, tends to inspissate 
the sap, 325 — solar, its influence on vegetable life, 41 — effects a 
decomposition of carbonic acid in plants, 41 — occasions the ex- 
trication of nitrogen in plants, 41 — promotes insensible perspi- 
ration in plants, 41, 48 — its full intensity can be safely borne by 
some species but not by others, 53 — more necessary than change 
of air in imparting flavour to fruits, 152. 

Lights of fruiting-houses, their removal, 156. 

Lignification depends on the action of leaves, 23 — sedimentary mat- 
ter of, 265. 

Lime, applied for the germination of seeds, 166 — enters into the 
organisation of plants, 335. 

Liquid manure, 340. 

M. 

Male flowers in unisexual plants, 82. 

Manures, 338 — their application, 340 — principles of their constitu- 
tion, 339 — their action, 340 — time of their application, 341 — 
manner of their application, 342 — liquid, 340. 

Marsh plants, 114. 

Maturation of fruit, 69. 

Medullary rays, 27. 

Melons, preservation of the purity of their races, 303 — effects of their 
roots being immersed in water, 116. 

Metallic substances in plants, 335, 336. 

Metamorphoses of the parts of plants, 57 — example of, 57, 61, 173. 

Mildew, 51, 123 — in wheat, attributed to a superabundant absorption 
of moisture, 51. 

Mineral substances in plants, 336. 

Moisture, atmospheric, when amounting to saturation, occasions a 
cessation of perspiration in plants, 48 — its absorption by leaves, 
51— connected with temperature, 125 — its range, 127— its mean 



354: INDEX. 

near London, 128 — effect of, on pollen, 171 — necessary to pro 
duce germination, 8 — of the soil, 113 — abundant supply of, re- 
quired by plants in a growing state, 114 — effects of an exces- 
sive supply of, 115 — of hothouses, its regulation, 142 — an excess 
of, prejudicial to plants in a rapid state of growth, 148 — rules 
for its adaptation, 149 — preserved by means of oiled paper, 155 
— necessary to germination, 160 — its tendency to produce decay 
in seeds, 163 — should be sparingly applied to the roots of trees 
previously too much dried, 294. 

Monstrosity a cause of sterility, 173 — causes inducing it, 316. 

Mules, their origin, 68. 

Muling, 310. 

Muling, limits of its operation, 312. 

Muriate of lime, its use for the preservation of seeds, 176. 

Muriate of soda, its free absorption by roots, 17. 

N. 

Nitrogen, in spongioles, 13 — in seeds, accelerates their vegetation, 19 
— indispensable for the first formation of tissue, 19 — a compo- 
nent of the food of plants, 18 — in plants, is extricated by solar 
light, 41 — its abundance in young tissue, 18. 

Night, diminution of the functions of plants in the, 327. 

Nodules in the bark of trees, 31. 

Nutritions matter, in plants, influences the production of flower-, 
buds, 65. 

O. 

Gleraceous annuals, 115. 

Orange tree, natural temperature of the soil for, 104. 

Orange tribe, drainage for their roots necessarily beneficial, 275. 

Ovary, and ovules, 56. 

Oxalic acid employed to promote the germination of old seeds, 167. 

Oxygen is absorbed from water during the process of germination. 8 
— in plants, 18 — derivation of its supply, 18 — excess of, in 
certain vegetable secretions, 75 — employed to promote germi- 
nation, 167 — is absorbed by leaves when their functions becoma 
languid through age, 54. 

P. 

Pan feeders, 269. 

Parasitical fungi supposed to lay hold of diseaeed tissue only, 51. 



INDEX. 355 

Paving the soil, 120. 

Peas, securing a late crop of, 124. 

Pendulous training, 260. 

Perspiration of plants supplied chiefly by the action of the spon- 
gioles, 13 — a function performed by the leaves of plants, 40 — is 
promoted by solar light, 41 — its amount in various species, 47- 
49 — experiments on, 47-49 — entirely obstructed when the air 
is saturated with moisture, 49 — its amount is in proportion to 
the intensity of the solar rays, 49 — commencement of its action, 
114 — an important vital function of plants, 126 — affected by 
wind, 129 — prevented by damp, 148 — excessive precautions 
against, 204 — cold produced by, 257 — through young bark, 283. 

Pine-apple, its habitat in a wild state, 232. 

Pine-apple stools, 210. 

Pines, grafting of, 237. 

Pistil, its parts and situation, 56. 

Pith, 28 — its production, 24 — in endogens is intermingled with the 
woody fibre, 24 — distinct and central in exogens, 24. 

Placenta, 76. 

Plant, its nature, 5 — mode of its birth detailed, 10. 

Plants, their power of producing roots from various parts, 14 — liable 
to injury from contact with deleterious matters in the soil, 17 — 
cannot exist long on pure water, 19 — the channel through which 
all their ascending fluids are conducted, 27 — their healthiness 
depends on the free action of the leaves, 40 — decompose car- 
bonic acid during the day, 42 — form carbonic acid during the 
night, 42 — inhabiting shady situations, reason of their not en- 
during full exposure to the sun. 44 — imbibe an excess of fluid 
during the night, 49 — their capacity of bearing direct light is 
variable in different species, 53 — deciduous, 54 — commencement 
of the period of their fructification, 63 — their limits of endurable 
temperature, 80 — are penetrated in all directions by air passages, 
102 — require a correspondence of temperature with that of the 
countries of which they are natives, 105 — of extreme climates, 
112 — growing on grass, 138— growing below projecting shelter, 
138 — in sitting-rooms, 148 — their cultivation in confined air, 
151 — have universally a season of rest, 319 — their resting, 319 
— their annual rest, 319 — diurnal rest, 327 — their rest neces- 
sary to flowering, 327 — some grow equally well in different 



356 INDEX. 

soils, and others av ill not, 332 — aphyllous, office of leaves per 
formed in, by the rind and epidermis, 40. 

Plumule, 22 — derives its nourishment partly from the cotyledons and 
partly through the agency of the root, 'J 2, 

Plunging of potted plants, 273. 

Poisonous substances fatal to man prove equally so to plants, 17. 

Poisons, alkaline, their destructive effects, 18 — metallic, destructive 
to plants, 18. 

Pollen, agents which affect its fertilising powers, 171 — deficiency of, 
a cause of sterility in seeds, 171. 

Potash, employed to promote germination, 166 — as a component of 
manures, 335, 338. 

Potato, tubers of, early varieties, their appropriation of nutritive 
matter, 173 — means of obtaining improved varieties of, 308 — 
unequal periods of its maturity from different eyes, 189. 

Potatoes, disease of, curl in the leaves of, 73 — propagation of, from 
eyes, 185. 

Pots for plants, their drainage, 119 — double, for plants, 274 — neces- 
sity of their being proportioned to the size of the plants, 277. 

Potting, 267 — objects attained by, 267 — eases in which it may be 
advantageously dispensed with, 268. 

Preservation of races by seed, 295. 

Pricking out seedlings, 268. 

Principles upon which the operations of horticulture essentially 
depend, 101. 

Productiveness, 64. 

Propagation by budding and grafting, only successful within certain 
degrees of affinity, 222 — its objects, 224, 228 — its rationale ex- 
plained, 199, 225 — by cuttings, 195 — by knaurs, 189 — by layers 
and suckers, 207 — by leaves, 189 — by eyes, 184 — by eyes and 
cuttings, difference of, from that by budding and grafting, 211 
— by roots, depends on the formation of adventitious buds, 20. 

Protection afforded by walls, 266. 

Pruning, 239— its objects, 239— its effects, 243— seasons for, 247 — of 
transplanted trees, 248 — of roots, 249. 

R. 

Races of plants, means of their preservation by seeds, 297 — means 

of fixing their habits, 297 — accidental alterations in, 307. 



INDEX. 357 

Races of plants, improvement of, 306. 

Radiation, 138. 

Radicle, 10. 

Rain, amount of, at various places, 128. 

Repotting, 2*72. 

Reproduction, property of, in leaf-buds, 7 — properties of, in seeds, 7. 

Respiration, a function performed by the leaves, 40. 

Rest of plants, 113 — periods of, in tropical regions, 321 — in tropical 
regions, how imitated, 326. 

Resting plants, 319. 

Rind, 26. 

Ringing, an operation by which the production of roots is accele- 
rated, 15 — experiments on, 34 — physiological nature of the 
operation, 252 — its effects on fructification, 65 — its use in facili- 
tating the production of roots, 208 — proper seasons for, 254 — 
its effects with regard to fruit and flowers, 254 — its ultimate 
consequences, 255. 

Ripening of seeds, 175. 

Root, substance from which it first derives its means of accretion, 
10 — is the part soonest developed, 10 — mode of its increase in 
length after it passes the embryo state, 1 1 — at first grows by a 
general distension of its tissue, 11 — offices of its bark, 12 — its 
proportion to the stem variable, 15. 

Roots lengthen at their points only, after passing their embryo 
state, 11 — why their extreme points are called spongelets, 11 — 
delicacy of their extreme points, 11 — their hygrometrical pro- 
perties, 1 1 — local motions of their spongioles in quest of fresh 
food, 13 — immediate cause of their formation involved in 
obscurity, 14 — produced from various parts of plants, 14 — aug- 
ment in diameter simultaneously with the stem, 14 — growing in 
air, 13 — growing in water, 13 — their formation, an elaboration 
of organisable matter furnished by the leaves, 15. 

Roots perish if their formation be not speedily followed by the 
development of leaves, 14 — most readily formed in darkness, 14 
— produced by removing a ring of bark, 15 — differ from 
branches in not being the development of previously formed 
buds, 14 — their incessant activity arrested only when frozen, 16 
— their principal office, 15 — their feeding property depends 
upon the hygrometrical force of their tissue, 16 — absorb gene- 



358 index. 

rally whatever is fluid and sufficiently attenuated, 16 — their 
property of throwing off secreted, deleterious, or superfluous 
matter, 19 — necessity of their advancing into fresh soil, 20 — in 
general haye no buds, 20 — of some species, their power oi 
forming adventitious buds, 20 — their fitness for propagation 
depends on their power of forming adventitious buds, 20 — 
effects of their being situated in a widely different temperature 
from that of the branches, 49 — their action reciprocal with 
that of the leaves, 49 — bad effects of their being deeply 
covered by soil, 105 — their deep penetration into cold soil, a 
cause of canker, 106 — are naturally placed in a higher mean 
temperature than branches and leaves, 107 — instances of their 
production by leaves, 190 — emitted into the air, 198 — are 
formed by the action of leaves, 199 — may be grafted, 225 — 
renovation of, 248 — pruning of, 249, 293 — their deleterious 
excretions, 270 — their slender power of selecting food, 270— 
their direction in pots, 272 — matted, 300 — bruised, 292— of 
trees retain the powers of life longer than branches, 19. 
Rose, double yellow, expansion of its flowers, 84. 

S. 

Saddle-grafting, 219. 

Salts, certain of them enter into the composition of the food of 
plants, 18. 

Sand, employed in propagation by cuttings, 203. 

Sap-wood, its mode of formation, 27. 

Sap, its constituents, 32 — its transmission through the stem, 32 — its 
changes during the course of its circulation, 32 — of plants may 
be made to deviate from its usual course, 33 — cause of its flow, 
36 — motion of, different from its flow, 36 — its ascending and 
descending currents communicate with different systems of 
veins in leaves. 36 — ascending, its force, 47 — derangement of its 
course, 49 — accumulation of, 72 — its circulation affected by 
motion communicated to plants by wind, 157 — may be com- 
pelled to organise itself externally as roots, 208 — direction 
given to, by pruning, 241 — its return obstructed by ringing, 
252 — an inspissated state of, produced by a dry atmosphere, 325. 

Saturation, hygrometrieal, 127. 

Scarring the centre of bulbs, 210. 



INDEX. 359 

Scion influenced by the stock, 224. 

Screens, 13*7 — their importance in moderating the dryness of the air, 
129 — of oiled paper, 155. 

Seasons of opposite extremes of moisture and dryness, 320. 

Secretion, saccharine, formed by the germinating seed, 10. 

Secretions of plants, formative agents of, 52 — an essential part of 
them formed by the decomposition of carbonic acid, 339 — of the 
fruit, 7 6 — changes which they undergo, 76 — result from the ac- 
tion of their leaves, 52 — table of the proportions of carbon and 
water in various, 75 — their formation favoured by a high tempe- 
rature, with dryness, 83 — decomposed by frost, 84 — of roots, 270. 

Seedlings, pricking out of, 268. 

Seed, its nature, 7 — its properties of reproduction, 7 — are different 
from those of leaf-buds, 7. 

Seeds contain an excess of carbon, 8 — manner of their germination, 8 
— conditions required to produce their germination, 8. 

Seeds, germinating, form a saccharine secretion, 9 — those germinate 
quickest which contain the most nitrogen, 20 — will renew the 
species, 68 — will not produce the identical peculiarities which cha- 
racterise varieties of the same species, 68 — origin of their food, 76 
— their longevity, 77 — its cause, 77 — destruction of their vitality, 
77 — remain dormant whilst their proportion of carbon is undis- 
turbed, 77 — difference in their vigour, 77, 161 — of tropical trees, 
degree of heat required for germination, 103 — length of time 
which some species of, will lie in the ground, 168 — consequences 
of gathering them in an unripe state, 175 — close packing of, in- 
jurious in hot climates, 182 — containing oily matter, 184 — ex- 
treme temperature which various species will bear, 162 — tem- 
perature required for their germination, 162 — cause of their rot- 
ting in the ground, 164 — vital energy of, 164 — with very hard 
integuments, means resorted to for assisting their germination, 
164 — old, of spruce fir, germination promoted in, 167 — germi- 
nating, effects produced upon, by alkaline substances, 166 — 
subjected to boiling, 165 — weak, produce weak plants, 174 — of 
composite plants, 174 — period of their retention of the power 
of germination, 175 — ripeness in, 175 — invigorated, 175 — their 
preservation, 177 — reproduce species only with certainty, 296 — 
preservation of races by, 296 — influence of circumstances under 
which they are matured extends to the progeny, 299. 



ObO INDEX. 

Seed-packing, 1*77. 

Seed-saving, 169. 

Seed-sowing, 159 — depth of seeds in the soil, 161. 

Sexes, the essential parts of a flower, 56. 

Shade necessary for cuttings, 205. 

Shifting plants in pots, 269. 

Shoots, young, their susceptibility of frost, 86 — " unripe," their di 
minished capability of resisting frost, 84. 

Silex in solution absorbed by the Wheat plant, 17 — rejected by th« 
Pea, 17. 

Situation of a garden, 137. 

Soil, necessity of roots advancing into fresh, 20 — sterile, its effects in 
accelerating fructification, 64 — its temperature and moisture 
more important than its niineralogical quality, 108 — moisture 
of the, 113 — its superior heat at top taken advantage of for the 
cure of canker, 106 — effects of one too wet, 115 — effects of rapid 
evaporation from, 120 — choice of, 137 — for seeds, 160 — its ex- 
haustion in pots, 269 — its deterioration by excretions of roots, 
270 — necessity of its being changed, 271. 

Soils, appropriation of stocks to, 230 — different, requisite for different 
varieties, 332. 

Solar light, difference of its effects on plants when transmitted 
through different coloured media, 206. 

Solar radiation cannot be imitated by bottom heat, so as to produce 
a similar effect, 94. 

Solar rays, their exhausting effects on plants, under certain circum- 
stances, 53 — the immediate cause of perspiration in plants, 
120. 

Spongelets, their consistence, 11 — reason of the extreme points of 
roots being so called, 11 — act as absorbents, 12 — are not special 
organs, 13 — their force of absorption, 15. 

Spongioles abound in nitrogen, 13 — chiefly supply the waste occa- 
sioned by perspiration, 13 — their importance, and the danger 
of destroying them, 13 — are not protected by a fully organised 
epidermis, 283. 

Succxilent plants, their small proportion of roots, 15. 

Succulents, 321. 

Suckers, propagation by, 207 — their production, 209 — of the Pine- 
apple, 209 



INDEX. 361 

Sulphuric acid, employed in drying air for the preservation of 3eed, 
176. 

Sulphurous acid gas, its escape from brick flues, 152 — its destructive 
effects, 152, 

Sun's rays, force of, 93, 

Superfluous matter thrown off by roots, 19, 

Stagnation of water about the roots of plants in pots, 275. 

Stamens, their parts and situation, 56 — their use, 68. 

Starch, its accumulation in seeds, 175. 

Stem bears a variable proportion to the roots, 15 — its origin, 21 — 
growth by the, 21 — is at first merely a small portion of cellular 
tissue, 2-1 — its parts, 25, 28 — its horizontal system, 24 — its per- 
pendicular system, 24— its property of forming leaf-buds, 30 — its 
office, 32. 

Stems, processes by which wounds in them are healed, 25 — those 
freely emitting roots may be more moulded up than others not 
possessing such power; 278, 

Sterility. 65 — from cold and moisture^ 84 — in seeds, causes of, 170 — 
remedy for, 173, 

Stigma, 56. 

Stocks, appropriation of. to soils, 230— their influence on grafts, 224 
— necessity of a correspondence in growth between their hori- 
zontal system and that of the graft or bud, 225 — their effects in 
modifying the growth of the tree, 226 — their effects on fructifi- 
cation, 227 — heading dowo, 234, 

Stomates, 38— their number and size proportionate to the natural 
habits of plants, 89 — number of, in a square inch of the leaves 
of various species, 39 — their position and adaptation, 51- — per- 
mit the escape of vapour, 115. 

Stones, utility of, in soil, 119. 

Strontian, rejected by certain plants, 17. 

Structure of flowers, 55. 

Style, 56. 

Syringing, 51. 

System, horizontal, of stems, 24, 26 — horizontal cellular, 24 — perpen- 
dicular, of stems, 24, 26. 

T. 
Temperature, effects of great discrepancy in, as regards different por- 



362 LXDEX. 

tions of a plant, 49 — limits of, endurable by plants, 80 — limit 
of, below which plants will not grow, 81 — effects of one too 
high on plants, 81 — unnaturally low, its effects, 83 — relatively 
high, conjoined with dryness, favours the formation of secre 
tions, 83 — at which different fluids become frozen, 85 — its laws 
with respect to its influence on vegetation, 87 — its alternations 
necessary to plants, 88 — of the earth at various places immedi 
ately below the surface, 91 — effects of its diurnal alternations, 
87 — effects of its annual alternations, 88 — of the earth, 90, 93 — 
at various places, comparatively with that of the atmosphere, 
91 — at various depths, 92 — of the hottest and coldest months at 
various places, 100 — importance of insuring a proper one for 
plants, 108 — of soils, its important influence on vegetation, 108 
— with regard to the direction of the wind, 130, 134 — of hot- 
houses, its regulation, 142 — effects of a high one at night in hot- 
houses, 145 — effects on pollen of one too low 171 — which grain 
will bear, 181 — seasons of extreme, 320 — uniform, 320 — low, 
with much light, its effects on the sap, 325 — of plant houses, ne- 
cessity of lowering it during the night, 328 — diurnal extremes 
of, 328. 

Tissue, general distension of, in the embryo state of roots, 9 — general 
distension of, in roots growing in air and water, 13 — its hygro- 
metrical force depends on the action of capillary tubes, 16. 

Tissue, its first formation requires nitrogen, 18 — disorganisation of, 
117 — impermeability of, induced by training, 265 — cellular, is 
the component of the first rudiments of the stem, 21. 

Tonguing, 217. 

Training, 257 — on a horizontal plane, bad effects of, 257 — its effects 
on the circulation of the juices, 259 — pendulous, 260 — its disad- 
vantages, 265. 

Transplanted trees, their pruning, 248 — languid from previous dry 
ness, effects on, by the too rapid absorption of water, 294. 

Transplanting, 279 — its rationale, 281 — season for, 283 — of deciduous 
trees, 280 — manner of performing the operation, 290 — prepara- 
tion of old trees for, 291. 

Trees and shrubs, distinct parts of their bark, 26. 

True sap, wholly generated in the leaves, 252, 

Tubers, 29. 



INDEX. 363 

u. 

Unisexual plants, effects of temperature on, 82 

V. 
"Valleys, superior general warmness of, 139 — their liability to sudden 

cold, 139. 
Vaporous impurities, 152. 
Varieties not absolutely permanent through propagation by seeds, 

296 — means of fixing them, 297 — contamination of, 302. 
Vegetation, relative advancement of, in stocks and scions, 234 — in 

forcing houses, mode of resting it, 330. 
Veins of leaves consist of two systems, 37 — their structure, 37. 
Ventilation, 150 — under some circumstances injurious, 151 — circum- 
stances which render it necessary, 152. 
Vine, its cultivation in the open air in England, cause of the general 

want of success in, 99 — great power of its ascending sap, 47 — 

preventive against its bleeding, 245 
Vine borders, their preparation, 119. 
Vines, a cause of their not setting, 106. 
Vital forces of vegetation, 40 — principle is stimulated by heat, 9, 107 

— principle in seeds, 175 — force in plants decomposes water, 40 

— functions of plants, 125. 
Vitality in seeds, causes of its destruction, 111. 

W. 

"Walls, effect of blackening, 138 — importance of, with regard to 
shelter, 131. 

Walnut, propagation of, by budding, 233. 

Water, a vehicle by which oxygen k supplied during the process of 
germination, 9 — in various respects conducive to germination, 9 
— enters into the composition of the food of plants, 18 — pure, 
cannot solely support vegetation for a long period, 18 — is de- 
composed by the vital action of plants, 18, 41 — proportions of, 
in certain vegetable secretions, 96 — an excessive supply of, re- 
tards the ripening of fruits, 76 — its decomposition or dissipation 
by fruits, 76 — in a tepid state applied to roots, 109 — in which 
aquatics are grown, necessity of regulating it to a due degree of 
temperature, 109 — in the soil, should be diminished when succu- 
lent fruit is ripening, 116 — stagnation of, 275 — absorption of, 



364 INDEX. 

by dried roots, effects of, 294 — effects of immersing roots in 
116. 

Watering* 113 — its effects on stiff soil, 122 — lias the effect of lower- 
ing the temperature of the soil, 122 — newly planted trees, 294 
— of roots, substitute for, under particular circumstances, 295. 

"Water plants, flowering of, 109. 

Weights applied to branches, 256 

Wet borders, 118. 

Whip-grafting, 210. 

Wind, its effect in increasing the dryness of the air, 129 — its effects 
with regard to fertilisation, 171 — its effect on the circulation of 
sap, 157. 

"Winds, table of, with the corresponding temperatures and dryness, 
133, 134. 

Winter of plants, not in all cases cold, 319. 

Wood formed by the combination of cellular tissue and woody fibre, 
23 — of exogens, 24 — the channel for the ascent of all the fluids 
of plants, 27 — of stems, 27 — central, its importance compared 
with that of the alburnum and liber, 33 — central, example of 
its removal, • 

Woody matter, its first appearance, 24. 

Worms, injury occasioned by them to plants in pots, 120. 

Wounding of plants to be avoided when the sap first begins to flow. 
244. 

Wounds, processes by which they are healed, 25, 292. 



THE END. 



